Read and write Ruby-marshalled data.
Only basics Ruby data types can be read and written:

  * `float`,
  * `bool`,
  * `int`,
  * `str` (mapped to `unicode` in Python 2),
  * `nil` (mapped to `None` in Python),
  * `array` (mapped to `list`),
  * `hash` (mapped to `dict`),
  * symbols and other classes are mapped to specific Python classes.