mechanize：Mechanize::Form#submit_button?

everyday Ruby

以下のような HTML で

<html>
<head>
<title>form test</title>
</head>
<body>

<form method="get" action="cgi/foo00.cgi" name="form1">
  <input type="submit" name="SUBMIT" value="Send" />　
  <input type="reset"  name="RESET"  value="Cancel" />
</form>

</body>
</html>
>> require 'mechanize'
=> true
>> agent = Mechanize.new
=> #<Mechanize:0xb747a538 ...
>> page = agent.get('http://127.0.0.1:8080/test18_button.html')
=> #<Mechanize::Page
 {url #<URI::HTTP:0xb7476bb8 URL:http://127.0.0.1:8080/test18_button.html>}
  ...
>> f = page.form('form1')
=> #<Mechanize::Form
  ...
>> f.submit_button?("SUBMIT")
=> true
>> f.submit_button?("RESET")
=> false
>> f.submit_button?("hoge")
=> false