code: def _check_valid_label(self, label):
          
          if len(label.shape) != 2 or label.shape[1] < 5:
              msg = "Label with shape (1+, 5+) required, %s received." % str(label)
              raise RuntimeError(msg)
          valid_label = np.where(np.logical_and(label[:, 0] >= 0, label[:, 3] > label[:, 1],
                                                label[:, 4] > label[:, 2]))[0]
          if valid_label.size < 1:
              raise RuntimeError('Invalid label occurs.')
docs: Validate label and its shape.