<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def find(self, selector, collation=None):
 """Specify selection criteria for bulk operations. :Parameters: - `selector` (dict):
 the selection criteria for update and remove operations. - `collation` (optional):
 An instance of :class:`~pymongo.collation.Collation`. This option is only supported on MongoDB 3.4 and above. :Returns: - A :class:`BulkWriteOperation` instance, used to add update and remove operations to this bulk operation. .. versionchanged:: 3.4 Added the `collation` option. """

        validate_is_mapping("selector", selector)
        return BulkWriteOperation(selector, self.__bulk, collation)