classes/Logging/ChannelManager.php
public function setDeferredChannel($channel, callable $callback)
	{
		if (isset($this->channels[$channel])) {
			throw new InvalidArgumentException("Channel $channel is already defined");
		}

		$this->deferredChannels[$channel] = $callback;
	}
public function setDeferredChannel($channel, callable $callback)
	{
		if (isset($this->channels[$channel])) {
			throw new InvalidArgumentException("Channel $channel is already defined");
		}

		$this->deferredChannels[$channel] = $callback;
	}
Define a deferred channel. The callback will be invoked and the return
value passed to setChannel. The return value must implement
Psr\Log\LoggerInterface.

@param string   $channel
@param callable $callback Callback that takes no arguments

@throws InvalidArgumentException If the channel is already defined.