in pybulletX/client.py [0:0]
def __init__(self, mode: int = None, client_id: int = None):
# should provide either mode or client_id but not both
# mode and client_id can't be both None at the same time.
# This is equiv. to XOR test
assert (mode is None) != (client_id is None)
if client_id is None:
self._initialized_by_us = True
self._id = px.init(mode=mode)
else:
self._initialized_by_us = False
self._id = client_id