code: def _validate_client(self, request, data):
          
          client = self.get_client(data.get('client_id'))
  
          if client is None:
              raise OAuthError({
                  'error': 'unauthorized_client',
                  'error_description': _("An unauthorized client tried to access"
                      " your resources.")
              })
  
          form = self.get_request_form(client, data)
  
          if not form.is_valid():
              raise OAuthError(form.errors)
  
          return client, form.cleaned_data
docs: :return: ``tuple`` - ``(client or False, data or error)``