'Start child process'

def start(self):

    assert (self._popen is None), 'cannot    start    a    process    twice'
    assert (self._parent_pid == os.getpid()), 'can    only    start    a    process    object    created    by    current    process'
    assert (not _current_process._daemonic), 'daemonic    processes    are    not    allowed    to    have    children'
    _cleanup()
    if (self._Popen is not None):
        Popen = self._Popen
    else:
        from .forking import Popen
    self._popen = Popen(self)
    _current_process._children.add(self)
