js/libs/ember-data.js
function(callback, binding) {
    get(this, 'relationshipsByName').forEach(function(name, relationship) {
      callback.call(binding, name, relationship);
    });
  }
function(callback, binding) {
    get(this, 'relationshipsByName').forEach(function(name, relationship) {
      callback.call(binding, name, relationship);
    });
  }
Given a callback, iterates over each of the relationships in the model,
invoking the callback with the name of each relationship and its relationship
descriptor.

@method eachRelationship
@static
@param {Function} callback the callback to invoke
@param {any} binding the value to which the callback's `this` should be bound