code: protected function normaliseSrcInput($input): array
      {
          $output = [];
  
          if ($input instanceof Finder)
          {
              foreach ($input as $fileInfo)
              {
                  $output[] = $fileInfo->getRealpath();
              }
          }
          else
          {
              if (!is_array($input)) $input = [$input];
  
              if (count($input) === 0) throw new \UnexpectedValueException;
  
              if (!is_string($input[0])) throw new \UnexpectedValueException;
  
              $output = $input;
          }
  
          return $output;
      }
docs: Helper method to convert several possible inputs
  to a simple array of file paths.
  
  @param  string|string[]|Finder $input Can be a single path to a folder or
  file, an array of files of folders,
  or a Finder instance.
  
  @return string[]