def METHOD_NAME(
    calls: list[building_blocks.Call], kind: str
) -> Optional[str]:
  if not calls:
    raise AssertionError('Expected `calls` to not be empty.')
  msg = 'Expected no {} aggregations, found {}:'.format(kind, len(calls))
  msg += ''.join(('\n\t' + call.compact_representation() for call in calls))
  raise AssertionError(msg)