def _handleSignals(self):
        """
        Extend the basic signal handling logic to also support
        handling SIGCHLD to know when to try to reap child processes.
        """
        _SignalReactorMixin._handleSignals(self)
        if platformType == 'posix' and processEnabled:
            if not self._childWaker:
                self._childWaker = _SIGCHLDWaker(self)
                self._internalReaders.add(self._childWaker)
                self.addReader(self._childWaker)
            self._childWaker.install()
            # Also reap all processes right now, in case we missed any
            # signals before we installed the SIGCHLD waker/handler.
            # This should only happen if someone used spawnProcess
            # before calling reactor.run (and the process also exited
            # already).
            process.reapAllProcesses()

        Extend the basic signal handling logic to also support
        handling SIGCHLD to know when to try to reap child processes.
        
stackoverflow/venv/lib/python3.6/site-packages/twisted/internet/posixbase.py