def _pipe_separated_uppercase(val):
  """
  Returns ``None`` if *val* is ``'*'``. Otherwise, split *val* on the ``'|'``
  character and return a list of the items, transformed to all caps.

  >>> _pipe_separated_uppercase("a|b|c")
  ['A', 'B', 'C']
  >>> _pipe_separated_uppercase("*")
  None
  """
  return None if val == '*' else set(s.upper() for s in val.split('|'))