code: def read_validate_params(self, request):
          
          self.client = self.client_authenticator.by_identifier_secret(request)
  
          self.password = request.post_param("password")
          self.username = request.post_param("username")
  
          self.scope_handler.parse(request=request, source="body")
  
          return True
docs: Checks if all incoming parameters meet the expected values.