'Check to see if the provided value is a valid choice'

def valid_value(self, value):

    for (k, v) in self.choices:
        if isinstance(v, (list, tuple)):
            for (k2, v2) in v:
                if (value == smart_unicode(k2)):
                    return True
        elif (value == smart_unicode(k)):
            return True
    return False
