# Set up before a parse.
	#
	# Before every parse, check whether the parent is
	# non-null, and re-register the filter for all of the
	# events.
	private fun setup_parse do
		assert parent_is_not_null: parent != 0 else
			sys.stderr.write("No parent for filter.")
		end
		parent.entity_resolver = self
		parent.dtd_handler = self
		parent.content_handler = self
		parent.error_handler = self
	end