How to use the pygraphviz.agraph.PipeReader function in pygraphviz

runprog=r'"%s"'%self._get_prog(prog)
        cmd=' '.join([runprog,args])
        dotargs = shlex.split(cmd)
        p = subprocess.Popen(dotargs,
                             shell=False,
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE,
                             close_fds=False)
        (child_stdin,
         child_stdout,
         child_stderr) = (p.stdin, p.stdout, p.stderr)
        # Use threading to avoid blocking
        data = []
        errors = []
        threads = [PipeReader(data, child_stdout),
                   PipeReader(errors, child_stderr)]
        for t in threads:
            t.start()
        self.write(child_stdin)
        child_stdin.close()
        for t in threads:
            t.join()

        if data==[]:
            raise IOError(b''.join(errors))

        if len(errors)>0:
            warnings.warn(b''.join(errors),RuntimeWarning)

        return b"".join(data)

cmd = ' '.join([runprog, args])
        dotargs = shlex.split(cmd)
        p = subprocess.Popen(dotargs,
                             shell=False,
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE,
                             close_fds=False)
        (child_stdin,
         child_stdout,
         child_stderr) = (p.stdin, p.stdout, p.stderr)
        # Use threading to avoid blocking
        data = []
        errors = []
        threads = [PipeReader(data, child_stdout),
                   PipeReader(errors, child_stderr)]
        for t in threads:
            t.start()

        self.write(child_stdin)
        child_stdin.close()

        for t in threads:
            t.join()
        p.wait()

        if not data:
            raise IOError(b"".join(errors).decode(self.encoding))

        if len(errors) > 0:
            warnings.warn(b"".join(errors).decode(self.encoding), RuntimeWarning)
        return b"".join(data)

cmd=' '.join([runprog,args])
        dotargs = shlex.split(cmd)
        p = subprocess.Popen(dotargs,
                             shell=False,
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE,
                             close_fds=False)
        (child_stdin,
         child_stdout,
         child_stderr) = (p.stdin, p.stdout, p.stderr)
        # Use threading to avoid blocking
        data = []
        errors = []
        threads = [PipeReader(data, child_stdout),
                   PipeReader(errors, child_stderr)]
        for t in threads:
            t.start()
        self.write(child_stdin)
        child_stdin.close()
        for t in threads:
            t.join()

        if data==[]:
            raise IOError(b''.join(errors))

        if len(errors)>0:
            warnings.warn(b''.join(errors),RuntimeWarning)

        return b"".join(data)

runprog = r'"%s"' % self._get_prog(prog)
        cmd = ' '.join([runprog, args])
        dotargs = shlex.split(cmd)
        p = subprocess.Popen(dotargs,
                             shell=False,
                             stdin=subprocess.PIPE,
                             stdout=subprocess.PIPE,
                             stderr=subprocess.PIPE,
                             close_fds=False)
        (child_stdin,
         child_stdout,
         child_stderr) = (p.stdin, p.stdout, p.stderr)
        # Use threading to avoid blocking
        data = []
        errors = []
        threads = [PipeReader(data, child_stdout),
                   PipeReader(errors, child_stderr)]
        for t in threads:
            t.start()

        self.write(child_stdin)
        child_stdin.close()

        for t in threads:
            t.join()
        p.wait()

        if not data:
            raise IOError(b"".join(errors).decode(self.encoding))

        if len(errors) > 0:
            warnings.warn(b"".join(errors).decode(self.encoding), RuntimeWarning)