code: def _add_logical_operator(self, operator):
          
  
          if not self.c_oper:
              raise QueryExpressionError("Logical operators must be preceded by an expression")
  
          self.current_field = None
          self.c_oper = None
  
          self.l_oper = inspect.currentframe().f_back.f_code.co_name
          self._query.append(operator)
          return self
docs: Adds a logical operator in query
  
          :param operator: logical operator (str)
          :raise:
              - QueryExpressionError: if a expression hasn't been set