code: function _linkOrCreateUser() {
      if(this.userInfo){ //If user exists link data
          return _linkIdentity(this.userInfo._id, 'instagram', this.options);
      }
      else {
          return _createUser.call(this)
                  .then(function(user){
                      this.userInfo = user;
                  }.bind(this));
      }
  }
docs: This function will take an social identity and assign it to a user.