Checks if a hash value for `key` exists.

@private
@name has
@memberOf Hash
@param {string} key The key of the entry to check.
@returns {boolean} Returns `true` if an entry for `key` exists, else `false`.
function hashHas(key) {
  var data = this.__data__;
  return nativeCreate ? (data[key] !== undefined) : hasOwnProperty$6.call(data, key);
}