def unlock! password=nil
      if password
        password = password.encode(Encoding::UTF_8)
        status = Sec.SecKeychainUnlock self, password.bytesize, password, 1
      else
        status = Sec.SecKeychainUnlock self, 0, nil, 0
      end
      Sec.check_osstatus status
    end
def unlock! password=nil
      if password
        password = password.encode(Encoding::UTF_8)
        status = Sec.SecKeychainUnlock self, password.bytesize, password, 1
      else
        status = Sec.SecKeychainUnlock self, 0, nil, 0
      end
      Sec.check_osstatus status
    end
Unlocks the keychain

 @param [optional, String] password the password to unlock the keychain with. If no password is supplied the keychain will prompt the user for a password