System.get_pid

You're seeing just the function get_pid, go back to System module for more information.
This function is deprecated. Use System.pid/0 instead.

Specs

get_pid() :: binary()

Erlang VM process identifier.

Returns the process identifier of the current Erlang emulator in the format most commonly used by the operating system environment.

For more information, see :os.getpid/0.