def check_tuple_size(tuples, tuple_size, context):
  """Helper function to check that the number of points in each tuple is
  equal to tuple_size (e.g. 2 for pairs), and raise a `ValueError` otherwise"""
  if tuple_size is not None and tuples.shape[1] != tuple_size:
    msg_t = (("Tuples of {} element(s) expected{}. Got tuples of {} "
             "element(s) instead (shape={}):\ninput={}.\n")
             .format(tuple_size, context, tuples.shape[1], tuples.shape,
                     tuples))
    raise ValueError(msg_t)