delete more unused code

lib/util/util.js

@@ -7,25 +7,6 @@ export function capitalizeFirstLetter(val) {
   return String(val).charAt(0).toUpperCase() + String(val).slice(1);
 }
 
-const _mapRecursiveStructure = mapping => transform => root => {
-  const found = mapping.get(root);
-  if (found) {
-    // already mapped
-    // return existing result to prevent endless recursion
-    return found;
-  }
-  // note the indirection (wrapped in lamda), this allows the user to recursively map the children (which may refer to the root) without yet having finished mapping the root.
-  let memo;
-  const result = () => {
-    // memoization is necessary for correctness
-    return memo || (memo = transform(root, _mapRecursiveStructure(mapping)(transform)));
-  };
-  mapping.set(root, result);
-  return result;
-};
-
-export const mapRecursiveStructure = _mapRecursiveStructure(new Map());
-
 export const memoize = callback => {
   let called = false
   let result;