'Build the <symbolicresponse> XML element.
Uses **kwargs:
*expect*: The correct answer (a sympy string)
*options*: list of option strings to pass to symmath_check
(e.g. \'matrix\', \'qbit\', \'imaginary\', \'numerical\')'

def create_response_element(self, **kwargs):

    expect = kwargs.get('expect', '')
    options = kwargs.get('options', [])
    options_str = ','.join(options)
    response_element = etree.Element('symbolicresponse')
    if expect:
        response_element.set('expect', str(expect))
    if options_str:
        response_element.set('options', str(options_str))
    return response_element
