# Look up a prefix and get the currently-mapped Namespace URI.
	#
	# This method looks up the prefix in the current context.
	# Use the empty string (`""`) for the default Namespace.
	#
	# Parameters:
	#
	# * `prefix`: The prefix to look up.
	#
	# Returns:
	#
	# The associated Namespace URI, or `null` if the prefix
	# is undeclared in this context.
	#
	# SEE: `prefix`
	#
	# SEE: `prefixes_of`
	fun uri(prefix: String): nullable String do
		return current_context.uri(prefix)
	end