code: def _parse(val_s, sep=_SEP):
      
      if (val_s.startswith('"') and val_s.endswith('"')) or \
              (val_s.startswith("'") and val_s.endswith("'")):
          return val_s[1:-1]
      if sep in val_s:
          return [P.parse(x) for x in P.parse_list(val_s)]
  
      return P.parse(val_s)
docs: FIXME: May be too naive implementation.
  
      :param val_s: A string represents some value to parse
      :param sep: separator between values
  
      >>> _parse(r'"foo string"')
      'foo string'
      >>> _parse("a, b, c")
      ['a', 'b', 'c']
      >>> _parse("aaa")
      'aaa'