code: def get_instance_field(self, field_name):
          
          if not self.has_field(field_name):
              raise AttributeError('"%s" is not a field for the model "%s"' %
                                   (field_name, self.__class__.__name__))
  
          field = getattr(self, field_name)
  
          return field
docs: Return the field object with the given name (works for a bound instance)