Error: only one Robot instance can be created per controller process.

[kazim27]

Describe the Bug
I am working on a Webots project in which four E-puck robots are used that push box to target locations with separate controller ,each controller consists of "Class Environment, class robot followed by main control loop"

_robot_instance = None
_supervisor_instance = None

def __init__(self, use_supervisor=False):
    self.use_supervisor = use_supervisor
    self.robot = None
    self.webots_supervisor = None
    self.TIME_STEP = 64

    if use_supervisor:
        if Environment._supervisor_instance is None:
            Environment._supervisor_instance = Supervisor()
        self.webots_supervisor = Environment._supervisor_instance
        self.robot = self.webots_supervisor.getFromDef("Agent1")
    else:
        if Environment._robot_instance is None:
            Environment._robot_instance = Robot()
        self.robot = Environment._robot_instance
        self.webots_supervisor = None

    self.time_step = self.robot.getBasicTimeStep() if not use_supervisor else None
def reset(self):
    print(f"Supervisor: {self.webots_supervisor}")
    # Release existing Robot/Supervisor instance if it exists
    if self.use_supervisor and Environment._supervisor_instance is not None:
        del Environment._supervisor_instance
    elif not self.use_supervisor and Environment._robot_instance is not None:
        del Environment._robot_instance
    # Create a new Robot/Supervisor instance
    if self.use_supervisor:
        Environment._supervisor_instance = Supervisor()
        self.webots_supervisor = Environment._supervisor_instance
        self.robot = self.webots_supervisor.getFromDef("Agent1")
    else:
        Environment._robot_instance = Robot()
        self.robot = Environment._robot_instance
        self.webots_supervisor = None
    try:
        # Corrected the Supervisor instance
        root = self.webots_supervisor.getRoot()
        self.print_node_names(root)

when I run it I end up getting an error like this: "Only one instance of the Robot class should be created per controller process"
I have been trying for days to solve the issue, but unfortunately, I am unable to figure it out. I would be grateful if you could provide me with some suggestions to help me solve the problem.