docs: def fmtinfo(value):
      """Returns (typetag, text, is_imprecise). Unlike other functions that operate
      on measurements, this also operates on bools, ints, and strings.
  
      """
      if value is None:
          raise ValueError('cannot format None!')
  
      if isinstance(value, text_type):
          return '', value, False
  
      if isinstance(value, bool):
          # Note: isinstance(True, int) = True, so this must come before the next case.
          if value:
              return 'b', 'y', False
          return 'b', '', False
  
      if isinstance(value, six.integer_types):
          return 'i', text_type(value), False
  
      if isinstance(value, float):
          return 'f', text_type(value), True
  
      if hasattr(value, '__pk_fmtinfo__'):
          return value.__pk_fmtinfo__()
  
      raise ValueError('don\'t know how to format %r as a measurement' % value)