def METHOD_NAME(parts, first_alt_index, suffixes):
  """Helper for _BraceExpand.
  Args:
    parts: input parts
    first_alt_index: index of the first BracedAltPart
    suffixes: List of suffixes to append.
  """
  out = []
  # Need to call _BraceExpand on each of the inner words too!
  first_alt = parts[first_alt_index]
  expanded_alts = []
  for w in first_alt.words:
    expanded_alts.extend(_BraceExpand(w.parts))
  prefix = parts[ : first_alt_index]
  for alt_parts in expanded_alts:
    for suffix in suffixes:
      out_parts = []
      out_parts.extend(prefix)
      out_parts.extend(alt_parts)
      out_parts.extend(suffix)
      # TODO: Do we need to preserve flags?
      out.append(out_parts)
  return out