How to generate g_a_hash (Telethon)

Question

I want to call a user in telegram using the telethon library, this is the code

async def call():
    client = TelegramClient('session', api_id, api_hash)
    await client.connect()
    result = await client(functions.phone.RequestCallRequest(
        user_id='username',
        g_a_hash=b'arbitrary\x7f data \xfa here',
        protocol=types.PhoneCallProtocol(
            min_layer=42,
            max_layer=42,
            library_versions=['some string here'],
            udp_p2p=True,
            udp_reflector=True
        ),
    ))
    print(result)
    await client.disconnect()

I am not sure what g_a_hash and library_versions are and how to generate them, I also searched online but couldn't find anything related to them, any help would be really appreciated!