How to use the circuits.handler function in circuits

    @handler("test", filter=True)
    def on_test(self, event, *args, **kwargs):
        self.events_executed.append('test_filter')
        return True

    @handler("values", priority=1.0)
    def _value2(self):
        return "bar"

    @handler("response_complete")
    def _on_response_complete(self, e, value):
        response = e.args[0]
        request = response.request
        if request.sock in self._codecs:
            self.fire(
                connect(
                    request.sock,
                    *request.sock.getpeername()
                ),
                self._wschannel
            )

	@handler("load")
	def onLOAD(self):
		"""C.onLOAD()

		Load the configuration file.
		"""

		self.read(self.filename)

self._p = Popen(
            command, shell=True, stdout=PIPE, stderr=PIPE,
            close_fds=True, preexec_fn=os.setsid
        )

        self._stdin = None
        if self._p.stdin is not None:
            self._stdin = File(self._p.stdin, channel="%s.stdin" % channel)
            self._stdin.register(self)

        self._stdout = File(self._p.stdout, channel="%s.stdout" % channel)
        self.addHandler(
            handler("eof", channel="%s.stdout" % channel)(self._on_stdout_eof)
        )
        self.addHandler(
            handler("read", channel="%s.stdout" % channel)(
                self._on_stdout_read
            )
        )
        self._stdout.register(self)

    @handler("read", target="stdin")
    def stdin_read(self, data):
        self.write(self.dest, data)

    @handler("read")
    def _on_read(self, data):
        self.__protocol.add_buffer(data)

    @handler("read")
    def on_read(self, sock, data):
        """Read Event Handler

        This is fired by the underlying Socket Component when there has been
        new data read from the connected client.

        ..note :: By simply returning, client/server socket components listen
                  to ValueChagned events (feedback) to determine if a handler
                  returned some data and fires a subsequent Write event with
                  the value returned.
        """

        return data

    @handler("email.header", "email.header.to")
    def _lookup_email_sender(self, event, *args, **kwargs):
        # event.artifact is a ThreatServiceArtifactDTO
        artifact_type = event.artifact['type']
        artifact_value = event.artifact['value']
        LOG.debug("_lookup_email_sender started for Artifact Type {0} - Artifact Value {1}".format(
            artifact_type, artifact_value))

        hits = self._query_hibp_api(artifact_value)

        yield hits

    @handler("write", target="ws")
    def _on_write(self, sock, data):
        payload = chr(0x00) + data.encode("utf-8") + chr(0xFF)
        self.push(Write(sock, payload))