Removing some TODOs

[czgdp1807]

Description of the problem

Currently the master has a TODO task of replacing the collections.deque with pydatastructs.Queue. We have decided not to do this replacement as queue is a very simple data structure and it's efficient implementation is already present in python. In fact, deepcopy.copy will be a bottleneck in doing this replacement so, we shouldn't simply invest our time in this.

Example of the problem

References/Other comments

[Riyagoel2]

I would like to contribute

[czgdp1807]

Sure, please proceed with a PR.

[Riyagoel2]

Can you please provide any reference

[czgdp1807]

For fixing this issue, you just have to look for lines in the codebase having TODO and remove those lines.