@classmethod
def create_param_doc(cls, param, prefix=None):
    """
        Generate documentation for single parameter of function
        :param param: dict contains info about parameter
        :param sub: prefix string for recursive purposes
        """
    desc = cls.exclude_html_reg.sub('', param['description']).strip()
    if not desc:
        desc = '<no description>'
    name = param['name']
    if prefix:
        name = '%s[%s]' % (prefix, name)
    doc_ = ':param %s: %s; %s' % (name, desc, param['validator'])
    if param['required']:
        doc_ += ' (REQUIRED)'
    else:
        doc_ += ' (OPTIONAL)'
    for param in param.get('params', []):
        doc_ += '\n' + cls.create_param_doc(param, name)
    return doc_
