def get_host_from_settings(self, index, variables=None, servers=None):
        """Gets host URL based on the index and variables
        :param index: array index of the host settings
        :param variables: hash of variable and the corresponding value
        :param servers: an array of host settings or None
        :return: URL based on host settings
        """
        if index is None:
            return self._base_path

        variables = {} if variables is None else variables
        servers = self.get_host_settings() if servers is None else servers

        try:
            server = servers[index]
        except IndexError:
            raise ValueError(
                "Invalid index {0} when selecting the host settings. "
                "Must be less than {1}".format(index, len(servers)))

        url = server['url']

        # go through variables and replace placeholders
        for variable_name, variable in server.get('variables', {}).items():
            used_value = variables.get(
                variable_name, variable['default_value'])

            if 'enum_values' in variable \
                    and used_value not in variable['enum_values']:
                raise ValueError(
                    "The variable `{0}` in the host URL has invalid value "
                    "{1}. Must be {2}.".format(
                        variable_name, variables[variable_name],
                        variable['enum_values']))

            url = url.replace("{" + variable_name + "}", used_value)

        return url
Gets host URL based on the index and variables
        :param index: array index of the host settings
        :param variables: hash of variable and the corresponding value
        :param servers: an array of host settings or None
        :return: URL based on host settings
        
lightly/openapi_generated/swagger_client/configuration.py