code: function parseRelations (data, relations, options) {
    var relationships = {}
  
    _.each(relations, function (relation, name) {
      var fkName = relation.keyTo
  
      // If relation is belongsTo then fk is the other way around
      if (utils.relationFkOnModelFrom(relation)) {
        fkName = relation.keyFrom
      }
  
      var pk = data[options.primaryKeyField]
      var fk = data[fkName]
  
      var toType = ''
      if (relation.polymorphic && utils.relationFkOnModelFrom(relation)) {
        var discriminator = relation.polymorphic.discriminator
        var model = options.app.models[data[discriminator]]
        toType = utils.pluralForModel(model)
      } else {
        toType = utils.pluralForModel(relation.modelTo)
      }
  
      // Relationship `links` should always be defined unless this is a
      // relationship request
      if (!options.isRelationshipRequest) {
        relationships[name] = {
          links: {
            related: options.host +
              options.restApiRoot +
              '/' +
              options.modelPath +
              '/' +
              pk +
              '/' +
              name
          }
        }
      }
  
      var relationship = null
  
      if (!_.isUndefined(fk) && relation.modelTo !== relation.modelFrom) {
        if (_.isArray(fk)) {
          relationship = makeRelations(toType, fk, options)
        } else {
          relationship = makeRelation(toType, fk, options)
        }
      }
  
      // No `data` key should be present unless there is actual relationship data.
      if (relationship) {
        relationships[name].data = relationship
      } else if (relation.type === 'belongsTo') {
        relationships[name].data = null
      }
    })
  
    return relationships
  }
docs: Parses relations from the request.
  @private
  @memberOf {Serializer}
  @param {Object} data
  @param {Object} relations
  @param {Object} options
  @return {Object}