src/select2.js
function(select2_data) {
          var model;
          if (opts.simple_tags) {
            model = [];
            angular.forEach(select2_data, function(value, index) {
              model.push(value.id);
            });
          } else {
            model = select2_data;
          }
          return model;
        }
function(select2_data) {
          var model;
          if (opts.simple_tags) {
            model = [];
            angular.forEach(select2_data, function(value, index) {
              model.push(value.id);
            });
          } else {
            model = select2_data;
          }
          return model;
        }
/*
Convert from Select2 view-model to Angular view-model.