A gstreamer.Poll keeps track of file descriptors much like fd_set (used with select()) or a struct pollfd array (used with poll()). Once created with Poll.new, the set can be used to wait for file descriptors to be readable and/or writable. It is possible to make this wait be controlled by specifying TRUE for the controllable flag when creating the set (or later calling Poll.setControllable).
Undocumented in source.