function getMapData(map, key) {
  var data = map.__data__;
  return isKeyable(key)
    ? data[typeof key == 'string' ? 'string' : 'hash']
    : data.map;
}
Gets the data for `map`.

@private
@param {Object} map The map to query.
@param {string} key The reference key.
@returns {*} Returns the map data.