For given node, it returns local part of the node,
i.e. the name of given attribute or element with namespace prefix removed.
If the argument is node-set, first node of the node-set will be considered.
Empty string is returned if the argument is an empty node-set, a node without
name or if the argument is not a node.If the argument is omitted, context node is used instead as if it is a node-set of one element.