Convenient way to create a new type by adding validation to existing type.

    Example: ::

        Ipv4Address = validated_type(
            String, 'Ipv4Address',
            # regexp simplified for demo purposes
            Regexp('^\d+\.\d+\.\d+\.\d+$', error='Invalid IP address')
        )

        Percentage = validated_type(Integer, validate=Range(0, 100))

        # The above is the same as

        class Ipv4Address(String):
            def __init__(self, *args, **kwargs):
                super(Ipv4Address, self).__init__(*args, **kwargs)
                self.validators.insert(0, Regexp('^\d+\.\d+\.\d+\.\d+$', error='Invalid IP address'))

        class Percentage(Integer):
            def __init__(self, *args, **kwargs):
                super(Percentage, self).__init__(*args, **kwargs)
                self.validators.insert(0, Range(0, 100))

    :param Type base_type: Base type for a new type.
    :param name str: Optional class name for new type
        (will be shown in places like repr).
    :param validate: A validator or list of validators for this data type.
        See `Type.validate` for details.

def validated_type(base_type, name=None, validate=None):
    """Convenient way to create a new type by adding validation to existing type.

    Example: ::

        Ipv4Address = validated_type(
            String, 'Ipv4Address',
            # regexp simplified for demo purposes
            Regexp('^\d+\.\d+\.\d+\.\d+$', error='Invalid IP address')
        )

        Percentage = validated_type(Integer, validate=Range(0, 100))

        # The above is the same as

        class Ipv4Address(String):
            def __init__(self, *args, **kwargs):
                super(Ipv4Address, self).__init__(*args, **kwargs)
                self.validators.insert(0, Regexp('^\d+\.\d+\.\d+\.\d+$', error='Invalid IP address'))

        class Percentage(Integer):
            def __init__(self, *args, **kwargs):
                super(Percentage, self).__init__(*args, **kwargs)
                self.validators.insert(0, Range(0, 100))

    :param Type base_type: Base type for a new type.
    :param name str: Optional class name for new type
        (will be shown in places like repr).
    :param validate: A validator or list of validators for this data type.
        See `Type.validate` for details.
    """
    if validate is None:
        validate = []
    if not is_sequence(validate):
        validate = [validate]

    class ValidatedSubtype(base_type):
        if name is not None:
            __name__ = name

        def __init__(self, *args, **kwargs):
            super(ValidatedSubtype, self).__init__(*args, **kwargs)
            for validator in reversed(validate):
                self.validators.insert(0, validator)

    return ValidatedSubtype