DataTypeBase init error caused by a bug in PR 563

[jiafatom]

I made a comment to PR 563, it will cause DataTypeBase init error, which breaks our onnxmltools pipeline
The detail is:
None should not be in format: should change to _DatatypeBase.__init__(self, "Dictionary", "Dictionary({})".format(repr(self.key_type)), None)

[1duo]

Fix has been merged. @jiafatom Let us know its still creating issue for onnxmltools pipeline. Thanks @jiafatom!