code: def validate(self, value):
          
          if self.required and not value:
              raise OAuthValidationError({'error': 'invalid_request'})
  
          # Validate that each value in the value list is in self.choices.
          for val in value:
              if not self.valid_value(val):
                  raise OAuthValidationError({
                      'error': 'invalid_request',
                      'error_description': _("'%s' is not a valid scope.") % \
                              val})
docs: Validates that the input is a list or tuple.