'Constructor must be able to take no args.
Args:
initializer: Optional parameter to construct from.
age: The age of this entry as an RDFDatetime. If not provided, create a
new instance.
Raises:
InitializeError: if we can not be initialized from this parameter.'

def __init__(self, initializer=None, age=None):

    if (age is None):
        age = RDFDatetime(age=0)
    self._age = age
    if (initializer.__class__ == self.__class__):
        self.ParseFromString(initializer.SerializeToString())
