Imports like Sequence, MutableSequence, etc. are deprecated since
python 3.3 and are removed from 3.8. This commit fixes these import
problems for users with python 3.8+
There seems to be a problem with the 2nd test involving python 3.5. Particularly, with cde data download command.
The rest of the tests yield good, so there shouldn't be any critical problems from this PR.
Didn't realize that there is a updated version of this repo which is being actively maintained for python versions 3.3 and up.
Closing this PR as it would be pointless to merge theses changes.
Imports like Sequence, MutableSequence, etc. are deprecated since python 3.3 and are removed from 3.8. This commit fixes these import problems for users with python 3.8+
ref: https://github.com/python/cpython/issues/81505