def create(cls, name, user_group=None, activation_date=None,
        expiration_date=None, comment=None):
        """
        Create an internal user. 
        Add a user example::
        
            InternalUser.create(name='goog', comment='my comment')
            
        :param str name: name of user that is displayed in SMC    
        :param list(str,InternalUserGroup) user_group: internal user groups
            which to add this user to.
        :param datetime activation_date: activation date as datetime object.
            Activation date only supports year and month/day
        :param datetime expiration_date: expiration date as datetime object.
            Expiration date only supports year and month/day
        :param str comment: optional comment
        :raises ElementNotFound: thrown if group specified does not exist
        :rtype: InternalUser
        """
        json = {
            'name': name,
            'unique_id': 'cn={},{}'.format(name, InternalUserDomain.user_dn),
            'comment': comment}
        
        limits = {'activation_date': activation_date, 'expiration_date': expiration_date}
        for attr, value in limits.items():
            json[attr] = datetime_to_ms(value) if value else None
            
        if user_group:
            json.update(user_group=element_resolver(user_group))

        return ElementCreator(cls, json)
Create an internal user. 
        Add a user example::
        
            InternalUser.create(name='goog', comment='my comment')
            
        :param str name: name of user that is displayed in SMC    
        :param list(str,InternalUserGroup) user_group: internal user groups
            which to add this user to.
        :param datetime activation_date: activation date as datetime object.
            Activation date only supports year and month/day
        :param datetime expiration_date: expiration date as datetime object.
            Expiration date only supports year and month/day
        :param str comment: optional comment
        :raises ElementNotFound: thrown if group specified does not exist
        :rtype: InternalUser