# File lib/mechanize/file_response.rb, line 35
  def [](key)
    return nil if key.casecmp('Content-Type') != 0
    return 'text/html' if directory?
    return 'text/html' if ['.html', '.xhtml'].any? { |extn|
      @file_path.end_with?(extn)
    }
    nil
  end