docs: def SetOperator(self, operator):
      """Sets the operator for this expression."""
      self.operator = operator
      # Find the appropriate list of operators for this attribute
      attribute_type = self.attribute_obj.GetRDFValueType()
      operators = attribute_type.operators
  
      # Do we have such an operator?
      self.number_of_args, self.operator_method = operators.get(
          operator, (0, None))
  
      if self.operator_method is None:
        raise lexer.ParseError("Operator %s not defined on attribute '%s'" %
                               (operator, self.attribute))
  
      self.operator_method = getattr(attribute_type, self.operator_method)