code: function resolveArgument(expr, argIndex) {
      if (typeof argIndex === 'undefined') {
          argIndex = 0;
      }
      if (!expr.arguments.length || !expr.arguments[argIndex]) {
          return;
      }
      this.applyPluginsBailResult('call require:commonjs:item', expr,
              this.evaluateExpression(expr.arguments[argIndex]));
  }
docs: Resolves module paths.
  @param  {Object} expr     The expression.
  @param  {Number} argIndex Which argument to resolve, defaults to the first arg.