'Return the attribute from the json data.
:param dict data: dictionary used to put together the model
:param str attribute: key of the attribute
:param any fallback: return value if original return value is falsy
:returns: value paired with key in dict, fallback'

@classmethod
def _get_attribute(cls, data, attribute, fallback=None):

    if ((data is None) or (not isinstance(data, dict))):
        return None
    result = data.get(attribute)
    if (result is None):
        return fallback
    return result
