def add_delete(self, selector, limit, collation=None):
        """Create a delete document and add it to the list of ops.
        """
        cmd = SON([('q', selector), ('limit', limit)])
        collation = validate_collation_or_none(collation)
        if collation is not None:
            self.uses_collation = True
            cmd['collation'] = collation
        if limit == _DELETE_ALL:
            # A bulk_write containing a delete_many is not retryable.
            self.is_retryable = False
        self.ops.append((_DELETE, cmd))
Create a delete document and add it to the list of ops.
        
stackoverflow/venv/lib/python3.6/site-packages/pymongo/bulk.py