code: function keysForDep(obj, depsMeta, depKey) {
    var keys = depsMeta[depKey];
    if (!keys) {
      // if there are no dependencies yet for a the given key
      // create a new empty list of dependencies for the key
      keys = depsMeta[depKey] = {};
    } else if (!depsMeta.hasOwnProperty(depKey)) {
      // otherwise if the dependency list is inherited from
      // a superclass, clone the hash
      keys = depsMeta[depKey] = o_create(keys);
    }
    return keys;
  }
docs: data structure: meta.deps = { 'depKey': { 'keyName': count, } } /*
  This function returns a map of unique dependencies for a
  given object and key.