code: function isForInRef(ref) {
              let target = ref.identifier.parent;
  
  
              // "for (var ...) { return; }"
              if (target.type === "VariableDeclarator") {
                  target = target.parent.parent;
              }
  
              if (target.type !== "ForInStatement") {
                  return false;
              }
  
              // "for (...) { return; }"
              if (target.body.type === "BlockStatement") {
                  target = target.body.body[0];
  
              // "for (...) return;"
              } else {
                  target = target.body;
              }
  
              // For empty loop body
              if (!target) {
                  return false;
              }
  
              return target.type === "ReturnStatement";
          }
docs: Determine if an identifier is used either in for-in loops.
  
  @param {Reference} ref - The reference to check.
  @returns {boolean} whether reference is used in the for-in loops
  @private