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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def save(self, to_save, manipulate=True, check_keys=True, **kwargs):
 """Save a document in this collection. **DEPRECATED** - Use :meth:`insert_one` or :meth:`replace_one` instead. .. versionchanged:: 3.0 Removed the `safe` parameter. Pass ``w=0`` for unacknowledged write operations. """

        warnings.warn("save is deprecated. Use insert_one or replace_one "
                      "instead", DeprecationWarning, stacklevel=2)
        common.validate_is_document_type("to_save", to_save)

        write_concern = None
        collation = validate_collation_or_none(kwargs.pop('collation', None))
        if kwargs:
            write_concern = WriteConcern(**kwargs)

        with self._socket_for_writes() as sock_info:
            if not (isinstance(to_save, RawBSONDocument) or "_id" in to_save):
                return self._insert(sock_info, to_save, True,
                                    check_keys, manipulate, write_concern)
            else:
                self._update(sock_info, {"_id": to_save["_id"]}, to_save, True,
                             check_keys, False, manipulate, write_concern,
                             collation=collation)
                return to_save.get("_id")