docs: def gen_key_input(self, key_params={}):
          '''
          Generate --gen-key input per gpg doc/DETAILS.
  
          :param key_params: Key parameters
          :rtype: str
          :return: Control input for :func:`regnupg.gen_key`
          '''
          params = self.default_key_params.copy()
          params.update(key_params)
          result = ['Key-Type: %s' % params.pop('Key-Type')]
          result += ('%s: %s' % (param, value) for param, value in params.items())
          result.append('%commit\n')
          return '\n'.join(result)