def _is_camel_case_abb(s, index):
  """Determine if the index ends at 'ABb', which is the start of a camel
    token. For example, with 'HTMLParser', this function detects 'LPa'."""
  return (index >= 2 and s[index - 2].isupper() and s[index - 1].isupper() and
          s[index].islower())