function debugStream( name, clbk ) {
		opts.name = name;
		if ( arguments.length > 1 ) {
			return new Stream( opts, clbk );
		}
		return new Stream( opts );
	}
Creates a transform stream for debugging stream pipelines.

@private
@param {string} name - debug namespace
@param {Callback} [clbk] - callback to invoke upon receiving data
@throws {TypeError} must provide valid options
@throws {TypeError} must provide a valid callback argument
@returns {DebugStream} debug stream