def resource(
        self,
        service_name,
        region_name=None,
        api_version=None,
        use_ssl=True,
        verify=None,
        endpoint_url=None,
        aws_access_key_id=None,
        aws_secret_access_key=None,
        aws_session_token=None,
        config=None,
    ):
        """
        Create a resource service client by name.

        :type service_name: string
        :param service_name: The name of a service, e.g. 's3' or 'ec2'. You
            can get a list of available services via
            :py:meth:`get_available_resources`.

        :type region_name: string
        :param region_name: The name of the region associated with the client.
            A client is associated with a single region.

        :type api_version: string
        :param api_version: The API version to use.  By default, botocore will
            use the latest API version when creating a client.  You only need
            to specify this parameter if you want to use a previous API version
            of the client.

        :type use_ssl: boolean
        :param use_ssl: Whether or not to use SSL.  By default, SSL is used.
            Note that not all services support non-ssl connections.

        :type verify: boolean/string
        :param verify: Whether or not to verify SSL certificates.  By default
            SSL certificates are verified.  You can provide the following
            values:

            * False - do not validate SSL certificates.  SSL will still be
              used (unless use_ssl is False), but SSL certificates
              will not be verified.
            * path/to/cert/bundle.pem - A filename of the CA cert bundle to
              uses.  You can specify this argument if you want to use a
              different CA cert bundle than the one used by botocore.

        :type endpoint_url: string
        :param endpoint_url: The complete URL to use for the constructed
            client. Normally, botocore will automatically construct the
            appropriate URL to use when communicating with a service.  You
            can specify a complete URL (including the "http/https" scheme)
            to override this behavior.  If this value is provided,
            then ``use_ssl`` is ignored.

        :type aws_access_key_id: string
        :param aws_access_key_id: The access key to use when creating
            the client.  This is entirely optional, and if not provided,
            the credentials configured for the session will automatically
            be used.  You only need to provide this argument if you want
            to override the credentials used for this specific client.

        :type aws_secret_access_key: string
        :param aws_secret_access_key: The secret key to use when creating
            the client.  Same semantics as aws_access_key_id above.

        :type aws_session_token: string
        :param aws_session_token: The session token to use when creating
            the client.  Same semantics as aws_access_key_id above.

        :type config: botocore.client.Config
        :param config: Advanced client configuration options. If region_name
            is specified in the client config, its value will take precedence
            over environment variables and configuration values, but not over
            a region_name value passed explicitly to the method.  If
            user_agent_extra is specified in the client config, it overrides
            the default user_agent_extra provided by the resource API. See
            `botocore config documentation
            <https://botocore.amazonaws.com/v1/documentation/api/latest/reference/config.html>`_
            for more details.

        :return: Subclass of :py:class:`~boto3.resources.base.ServiceResource`
        """
        try:
            resource_model = self._loader.load_service_model(
                service_name, 'resources-1', api_version
            )
        except UnknownServiceError:
            available = self.get_available_resources()
            has_low_level_client = (
                service_name in self.get_available_services()
            )
            raise ResourceNotExistsError(
                service_name, available, has_low_level_client
            )
        except DataNotFoundError:
            # This is because we've provided an invalid API version.
            available_api_versions = self._loader.list_api_versions(
                service_name, 'resources-1'
            )
            raise UnknownAPIVersionError(
                service_name, api_version, ', '.join(available_api_versions)
            )

        if api_version is None:
            # Even though botocore's load_service_model() can handle
            # using the latest api_version if not provided, we need
            # to track this api_version in boto3 in order to ensure
            # we're pairing a resource model with a client model
            # of the same API version.  It's possible for the latest
            # API version of a resource model in boto3 to not be
            # the same API version as a service model in botocore.
            # So we need to look up the api_version if one is not
            # provided to ensure we load the same API version of the
            # client.
            #
            # Note: This is relying on the fact that
            #   loader.load_service_model(..., api_version=None)
            # and loader.determine_latest_version(..., 'resources-1')
            # both load the same api version of the file.
            api_version = self._loader.determine_latest_version(
                service_name, 'resources-1'
            )

        # Creating a new resource instance requires the low-level client
        # and service model, the resource version and resource JSON data.
        # We pass these to the factory and get back a class, which is
        # instantiated on top of the low-level client.
        if config is not None:
            if config.user_agent_extra is None:
                config = copy.deepcopy(config)
                config.user_agent_extra = 'Resource'
        else:
            config = Config(user_agent_extra='Resource')
        client = self.client(
            service_name,
            region_name=region_name,
            api_version=api_version,
            use_ssl=use_ssl,
            verify=verify,
            endpoint_url=endpoint_url,
            aws_access_key_id=aws_access_key_id,
            aws_secret_access_key=aws_secret_access_key,
            aws_session_token=aws_session_token,
            config=config,
        )
        service_model = client.meta.service_model

        # Create a ServiceContext object to serve as a reference to
        # important read-only information about the general service.
        service_context = boto3.utils.ServiceContext(
            service_name=service_name,
            service_model=service_model,
            resource_json_definitions=resource_model['resources'],
            service_waiter_model=boto3.utils.LazyLoadedWaiterModel(
                self._session, service_name, api_version
            ),
        )

        # Create the service resource class.
        cls = self.resource_factory.load_from_definition(
            resource_name=service_name,
            single_resource_json_definition=resource_model['service'],
            service_context=service_context,
        )

        return cls(client=client)

        Create a resource service client by name.

        :type service_name: string
        :param service_name: The name of a service, e.g. 's3' or 'ec2'. You
            can get a list of available services via
            :py:meth:`get_available_resources`.

        :type region_name: string
        :param region_name: The name of the region associated with the client.
            A client is associated with a single region.

        :type api_version: string
        :param api_version: The API version to use.  By default, botocore will
            use the latest API version when creating a client.  You only need
            to specify this parameter if you want to use a previous API version
            of the client.

        :type use_ssl: boolean
        :param use_ssl: Whether or not to use SSL.  By default, SSL is used.
            Note that not all services support non-ssl connections.

        :type verify: boolean/string
        :param verify: Whether or not to verify SSL certificates.  By default
            SSL certificates are verified.  You can provide the following
            values:

            * False - do not validate SSL certificates.  SSL will still be
              used (unless use_ssl is False), but SSL certificates
              will not be verified.
            * path/to/cert/bundle.pem - A filename of the CA cert bundle to
              uses.  You can specify this argument if you want to use a
              different CA cert bundle than the one used by botocore.

        :type endpoint_url: string
        :param endpoint_url: The complete URL to use for the constructed
            client. Normally, botocore will automatically construct the
            appropriate URL to use when communicating with a service.  You
            can specify a complete URL (including the "http/https" scheme)
            to override this behavior.  If this value is provided,
            then ``use_ssl`` is ignored.

        :type aws_access_key_id: string
        :param aws_access_key_id: The access key to use when creating
            the client.  This is entirely optional, and if not provided,
            the credentials configured for the session will automatically
            be used.  You only need to provide this argument if you want
            to override the credentials used for this specific client.

        :type aws_secret_access_key: string
        :param aws_secret_access_key: The secret key to use when creating
            the client.  Same semantics as aws_access_key_id above.

        :type aws_session_token: string
        :param aws_session_token: The session token to use when creating
            the client.  Same semantics as aws_access_key_id above.

        :type config: botocore.client.Config
        :param config: Advanced client configuration options. If region_name
            is specified in the client config, its value will take precedence
            over environment variables and configuration values, but not over
            a region_name value passed explicitly to the method.  If
            user_agent_extra is specified in the client config, it overrides
            the default user_agent_extra provided by the resource API. See
            `botocore config documentation
            <https://botocore.amazonaws.com/v1/documentation/api/latest/reference/config.html>`_
            for more details.

        :return: Subclass of :py:class:`~boto3.resources.base.ServiceResource`
        
boto3/session.py