code: def _check_backend(self, backend, endpoint):
          
          # First check against hacks for old backend names
          original_backend = backend
          backend = backend.lower()
          if endpoint == 'experiment':
              if backend in self.__names_backend_ibmqxv2:
                  return 'real'
              elif backend in self.__names_backend_ibmqxv3:
                  return 'ibmqx3'
              elif backend in self.__names_backend_simulator:
                  return 'sim_trivial_2'
  
          # Check for new-style backends
          backends = self.available_backends()
          for backend in backends:
              if backend['name'] == original_backend:
                return original_backend
          # backend unrecognized
          return None
docs: Check if the name of a backend is valid to run in QX Platform