'Initialize Type validator.
Args:
expected_type: Type that attribute should validate against.
convert: Cause conversion if value is not the right type.
Conversion is done by calling the constructor of the type
with the value as its first parameter.
default: Default assignment is made during initialization and will
not pass through validation.'

def __init__(self, expected_type, convert=True, default=None):

    super(Type, self).__init__(default)
    self.expected_type = expected_type
    self.convert = convert
