function getFunctionName( node ) {
	if ( !node ) {
		return '';
	}
	if ( node.type === 'MemberExpression' ) {
		return getFunctionName( node.object ) + '_' + node.property.name;
	}
	if ( node.type === 'Identifier' ) {
		return node.name;
	}
	return '';
}
Resolves the function name associated with a provided AST node.

@private
@param {Object} node - ast node
@returns {string} function name representing the node