code: def add_clause(self, clause):
          
          if clause.query_loc == MongoClause.LOC_MAIN:
              self._main.append(clause)
          elif clause.query_loc == MongoClause.LOC_MAIN2:
              self._main2.append(clause)
          elif clause.query_loc == MongoClause.LOC_WHERE:
              self._where.append(clause)
          else:
              raise RuntimeError('bad clause location: {}'.format(clause.query_loc))
docs: Add a new clause to the existing query.
  
          :param clause: The clause to add
          :type clause: MongoClause
          :return: None