This is the gr-vocoder package. It contains all available vocoders in GNU Radio. The Python namespaces is in gnuradio.vocoder, which would be normally imported as:
See the Doxygen documentation for details about the blocks available in this package.
A quick listing of the details can be found in Python after importing by using:
Note that most vocoders use short inputs instead of floats. This means you must convert audio signals from float to short by using a type conversion and a scaling factor. See the examples.
The format of the encoded audio is different for every encoder. See the individual block's documentation for the data format. Encoded data is usually a vector of fixed length, and can either be packed or unpacked.