# Report an XML comment anywhere in the document.
	#
	# This callback will be used for comments inside or outside the
	# document element, including comments in the external DTD
	# subset (if read). Comments in the DTD must be properly
	# nested inside `start/end_dtd` and `start/end_entity` events (if
	# used).
	#
	# Parameters:
	#
	# * `str`: characters in the comment.
	fun comment(str: String) do end