Returns a 2-tuple of the timestamp columns that were found on the table definition.

def get_timestamps(cols, created_name, updated_name):
  """Returns a 2-tuple of the timestamp columns that were found on the table definition."""
  has_created = created_name in cols
  has_updated = updated_name in cols
  return (created_name if has_created else None, updated_name if has_updated else None)