'Return the callback namedtuple to represent the specified callback.
Args:
callback (dict): the callback definition.
The callback given in argument should be a dictionary containing
the expected fields for a callback (code, author, valid...).'

@staticmethod
def format_callback(callback):

    if ('obj' not in callback):
        callback['obj'] = None
    if ('name' not in callback):
        callback['name'] = 'unknown'
    if ('number' not in callback):
        callback['number'] = (-1)
    if ('code' not in callback):
        callback['code'] = ''
    if ('author' not in callback):
        callback['author'] = None
    if ('valid' not in callback):
        callback['valid'] = False
    if ('parameters' not in callback):
        callback['parameters'] = ''
    if ('created_on' not in callback):
        callback['created_on'] = None
    if ('updated_by' not in callback):
        callback['updated_by'] = None
    if ('updated_on' not in callback):
        callback['updated_on'] = None
    return Callback(**callback)
