def group(self, key, condition, initial, reduce, finalize=None, **kwargs):
        """Perform a query similar to an SQL *group by* operation.

        **DEPRECATED** - The group command was deprecated in MongoDB 3.4. The
        :meth:`~group` method is deprecated and will be removed in PyMongo 4.0.
        Use :meth:`~aggregate` with the `$group` stage or :meth:`~map_reduce`
        instead.

        .. versionchanged:: 3.5
           Deprecated the group method.
        .. versionchanged:: 3.4
           Added the `collation` option.
        .. versionchanged:: 2.2
           Removed deprecated argument: command
        """
        warnings.warn("The group method is deprecated and will be removed in "
                      "PyMongo 4.0. Use the aggregate method with the $group "
                      "stage or the map_reduce method instead.",
                      DeprecationWarning, stacklevel=2)
        group = {}
        if isinstance(key, string_type):
            group["$keyf"] = Code(key)
        elif key is not None:
            group = {"key": helpers._fields_list_to_dict(key, "key")}
        group["ns"] = self.__name
        group["$reduce"] = Code(reduce)
        group["cond"] = condition
        group["initial"] = initial
        if finalize is not None:
            group["finalize"] = Code(finalize)

        cmd = SON([("group", group)])
        collation = validate_collation_or_none(kwargs.pop('collation', None))
        cmd.update(kwargs)

        with self._socket_for_reads(session=None) as (sock_info, slave_ok):
            return self._command(sock_info, cmd, slave_ok,
                                 collation=collation,
                                 user_fields={'retval': 1})["retval"]
Perform a query similar to an SQL *group by* operation.

        **DEPRECATED** - The group command was deprecated in MongoDB 3.4. The
        :meth:`~group` method is deprecated and will be removed in PyMongo 4.0.
        Use :meth:`~aggregate` with the `$group` stage or :meth:`~map_reduce`
        instead.

        .. versionchanged:: 3.5
           Deprecated the group method.
        .. versionchanged:: 3.4
           Added the `collation` option.
        .. versionchanged:: 2.2
           Removed deprecated argument: command
        
stackoverflow/venv/lib/python3.6/site-packages/pymongo/collection.py