code: public function getProgress()
      {
          if (null === $this->progress) {
              if (OutputInterface::VERBOSITY_VERBOSE <= $this->options['verbosity'] && 'txt' === $this->getFormat()) {
                  $progressType = $this->options['show-progress'];
                  $progressTypes = ['none', 'run-in', 'estimating', 'estimating-max', 'dots'];
  
                  if (null === $progressType) {
                      $default = 'run-in';
  
                      if (getenv('PHP_CS_FIXER_FUTURE_MODE')) {
                          $default = 'dots';
                      }
  
                      $progressType = $this->getConfig()->getHideProgress() ? 'none' : $default;
                  } elseif (!\in_array($progressType, $progressTypes, true)) {
                      throw new InvalidConfigurationException(sprintf(
                          'The progress type "%s" is not defined, supported are "%s".',
                          $progressType,
                          implode('", "', $progressTypes)
                      ));
                  } elseif (\in_array($progressType, ['estimating', 'estimating-max', 'run-in'], true)) {
                      $message = 'Passing `estimating`, `estimating-max` or `run-in` is deprecated and will not be supported in 3.0, use `none` or `dots` instead.';
  
                      if (getenv('PHP_CS_FIXER_FUTURE_MODE')) {
                          throw new \InvalidArgumentException("{$message} This check was performed as `PHP_CS_FIXER_FUTURE_MODE` env var is set.");
                      }
  
                      @trigger_error($message, E_USER_DEPRECATED);
                  }
  
                  $this->progress = $progressType;
              } else {
                  $this->progress = 'none';
              }
          }
  
          return $this->progress;
      }
docs: @throws InvalidConfigurationException
  
  @return string