Python 3.10 compatibility - Use of deprecated alias to Collections.abc.Sequence

[delta1513]

Just stumbled upon this project and decided to take it for a little spin when I found that I was getting this error when trying out the truth tables tutorial:

>>> X = exprvars('x', 3)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/mark/.local/lib/python3.10/site-packages/pyeda/boolalg/bfarray.py", line 201, in exprvars
    return _vars(Expression, name, *dims)
  File "/home/mark/.local/lib/python3.10/site-packages/pyeda/boolalg/bfarray.py", line 976, in _vars
    return farray(objs, shape, ftype)
  File "/home/mark/.local/lib/python3.10/site-packages/pyeda/boolalg/bfarray.py", line 430, in __init__
    self._items, autoshape, autoftype = _itemize(objs)
  File "/home/mark/.local/lib/python3.10/site-packages/pyeda/boolalg/bfarray.py", line 1032, in _itemize
    if not isinstance(objs, collections.Sequence):
AttributeError: module 'collections' has no attribute 'Sequence'

Looks like an easy fix, might even make a fork and PR myself but going from Python 3.9 to 3.10, the aliases to Collections.abc.* have been removed from Collections.* as shown here and in the docs.

Feel free to assign me to this issue and I'll have a PR made soon.

[delta1513]

I just realised that this was already in a PR ( #167 ) so it looks like it was the fact that the PyPi package was not updated (?)

I'll build manually and close this issue if it works.