code: protected function ensureFileIsReadable()
      {
          if (!is_readable($this->filePath) || !is_file($this->filePath)) {
              throw new UnableReadFileException(sprintf('Unable to read the file at %s.', $this->filePath));
          }
      }
docs: Ensures the given file is readable.
  
  @throws \Jackiedo\DotenvEditor\Exceptions\UnableReadFileException
  
  @return void