RuntimeError: An attempt has been made to start a new process before the current process has finished its bootstrapping phase. This probably means that you are not using fork to start your child processes and you have for

This error occurs when you try to create a new process using the `multiprocessing` module before the current process has finished initializing. It usually happens when you try to use the `multiprocessing` module in an interactive environment like Jupyter Notebook or IPython.

To fix this error, you can wrap your code in a `if __name__ == '__main__':` block. This ensures that the code inside the block is only executed when the script is run as the main program, and not when it is imported as a module.

For example:

import multiprocessing

def my_func():
    print("Hello from a child process")

if __name__ == '__main__':
    p = multiprocessing.Process(target=my_func)
    p.start()
    p.join()

This code defines a function `my_func()` that will be executed in a new process. The `if __name__ == '__main__':` block ensures that the new process is only created when the script is run as the main program.