code: def _jwt_required(realm):
      
      token = _jwt.request_callback()
  
      if token is None:
          raise JWTError('Authorization Required', 'Request does not contain an access token',
                         headers={'WWW-Authenticate': 'JWT realm="%s"' % realm})
  
      try:
          payload = _jwt.jwt_decode_callback(token)
      except jwt.InvalidTokenError as e:
          raise JWTError('Invalid token', str(e))
  
      _request_ctx_stack.top.current_identity = identity = _jwt.identity_callback(payload)
  
      if identity is None:
          raise JWTError('Invalid JWT', 'User does not exist')
docs: Does the actual work of verifying the JWT data in the current request.
      This is done automatically for you by `jwt_required()` but you could call it manually.
      Doing so would be useful in the context of optional JWT access in your APIs.
  
      :param realm: an optional realm