code: function mergeDefaults(objValue, srcValue, key, object, source, stack) {
          if (isObject(objValue) && isObject(srcValue)) {
            baseMerge(objValue, srcValue, undefined, mergeDefaults, stack.set(srcValue, objValue));
          }
          return objValue;
        }
docs: Used by `_.defaultsDeep` to customize its `_.merge` use.
  
  @private
  @param {*} objValue The destination value.
  @param {*} srcValue The source value.
  @param {string} key The key of the property to merge.
  @param {Object} object The parent object of `objValue`.
  @param {Object} source The parent object of `srcValue`.
  @param {Object} [stack] Tracks traversed source values and their merged counterparts.
  @returns {*} Returns the value to assign.