docs: 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
          self.ops.append((_DELETE, cmd))