# Create a new input source with the specified system identifier.
	#
	# Applications may use `public_id=` to include a public identifier as well,
	# or `encoding=` to specify the character encoding, if known.
	#
	# If the system identifier is a URL, it must be fully resolved (it may not
	# be a relative URL).
	init with_system_id(system_id: String) do
		self.system_id = system_id
	end