<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def build_response_card(title, subtitle, options):
 """ Build a responseCard with a title, subtitle, and an optional set of options which should be displayed as buttons. """

    buttons = None
    if options is not None:
        buttons = []
        for i in range(min(5, len(options))):
            buttons.append(options[i])

    return {
        'contentType': 'application/vnd.amazonaws.card.generic',
        'version': 1,
        'genericAttachments': [{
            'title': title,
            'subTitle': subtitle,
            'buttons': buttons
        }]
    }