code: function getRequiredModuleName(node) {
      var moduleName;
  
      // node has arguments and first argument is string
      if (node.arguments.length && isString(node.arguments[0])) {
        var argValue = path.basename(node.arguments[0].value.trim());
  
        // check if value is in required modules array
        if (requiredModules.indexOf(argValue) !== -1) {
          moduleName = argValue;
        }
      }
  
      return moduleName;
    }
docs: Function to check if a node has an argument that is a required module and
  return its name.
  @param {ASTNode} node The node to check
  @returns {undefined|String} required module name or undefined