code: function _singleCopy(sourceRef, copyRef, rc) {
      return _instanceCopy(sourceRef, copyRef, rc, (item, val, key) => {
          copyRef[key] = _clone(val, rc);
      });
  }
docs: Copies data from one item to another.
  Designed to a be a generic copy interface, where possible.
  
  @param sourceRef A reference to the source.
  @param copyRef A reference to the copy.
  @param rc The current recurse and reference counter.
  @returns {any} The reference to the copy.