code: def _validate_indexers(self, key):
          
          for dim, k in zip(self.dims, key):
              if isinstance(k, BASIC_INDEXING_TYPES):
                  pass
              else:
                  if not isinstance(k, Variable):
                      k = np.asarray(k)
                      if k.ndim > 1:
                          raise IndexError(
                              "Unlabeled multi-dimensional array cannot be "
                              "used for indexing: {}".format(k))
                  if k.dtype.kind == 'b':
                      if self.shape[self.get_axis_num(dim)] != len(k):
                          raise IndexError(
                              "Boolean array size {0:d} is used to index array "
                              "with shape {1:s}.".format(len(k),
                                                         str(self.shape)))
                      if k.ndim > 1:
                          raise IndexError("{}-dimensional boolean indexing is "
                                           "not supported. ".format(k.ndim))
                      if getattr(k, 'dims', (dim, )) != (dim, ):
                          raise IndexError(
                              "Boolean indexer should be unlabeled or on the "
                              "same dimension to the indexed array. Indexer is "
                              "on {0:s} but the target dimension is "
                              "{1:s}.".format(str(k.dims), dim))
docs: Make sanity checks