Add ports

[rsetaluri]

TODO: add tests

[coveralls]

Pull Request Test Coverage Report for Build 1811

• 30 of 31 (96.77%) changed or added relevant lines in 2 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.09%) to 73.031%

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Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
magma/circuit.py	13	14	92.86%

Totals
Change from base Build 1796:	0.09%
Covered Lines:	4154
Relevant Lines:	5688

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💛 - Coveralls

[leonardt]

LGTM, the only concern I have would be that this keeps instance objects around indefinitely so long as the class is alive because it maintains a reference. I think Python's weakref would allow us to mitigate this issue: https://docs.python.org/3/library/weakref.html

[leonardt]

@rsetaluri what do you think about improving the logic to use weakref? I thought about it more, and this is mainly an issue when we add the notion of deleting instances (because then the class will hold the remaining reference), but in theory it could still manifest in the current code when a Circuit object goes out of scope (it will get destructed, releasing it's reference to it's placed instances, however those placed instances won't get cleaned up because their definition class still maintains a reference to them).

[rsetaluri]

This is stale. We will revisit this feature in the future properly.