added plot_probabilities method in result class

[EmilianoG-byte]

Description

• Added a plot_probabilities method under the result class
• Nice and easy visualisation of the probabilities obtained for the basis states after the optimisation workflow.
• works for both state vector and shot based back-ends
• note: can add an additional argument to decide whether to plot states with zero probability or not.

Checklist

• I have performed a self-review of my code.
• I have commented my code and used numpy-style docstrings
• I have made corresponding updates to the documentation.
• My changes generate no new warnings
• I have added/updated tests to make sure bugfix/feature works.
• New and existing unit tests pass locally with my changes.

Type of change

Please delete options that are not relevant.

• New feature (non-breaking change which adds functionality)
• This change requires a documentation update

How Has This Been Tested?

Via UnitTest in the test_result_object.py file. Both for 'vectored' and 'qiskit.shot_simulator'.

[codecov]

Codecov Report

Merging #82 (18d063b) into dev (431b683) will decrease coverage by 3.35%.
The diff coverage is 81.05%.

@@            Coverage Diff             @@
##              dev      #82      +/-   ##
==========================================
- Coverage   92.84%   89.48%   -3.36%     
==========================================
  Files          60       63       +3     
  Lines        7629     8150     +521     
==========================================
+ Hits         7083     7293     +210     
- Misses        546      857     +311     

Impacted Files	Coverage Δ
openqaoa/backends/qaoa_backend.py	70.27% <ø> (ø)
openqaoa/backends/simulators/qaoa_qiskit_sim.py	100.00% <ø> (ø)
openqaoa/basebackend.py	86.80% <ø> (ø)
openqaoa/qaoa_parameters/gatemap.py	88.02% <0.00%> (ø)
openqaoa/qaoa_parameters/operators.py	100.00% <ø> (ø)
openqaoa/workflows/optimizer.py	83.33% <ø> (ø)
setup.py	100.00% <ø> (ø)
tests/test_results.py	100.00% <ø> (ø)
tests/test_qpu_qiskit.py	11.01% <23.52%> (ø)
openqaoa/cost_function.py	60.00% <28.57%> (-3.64%)	⬇️
... and 23 more

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[Q-lds]

Ok! Besides the potential issue regarding the Pauli op error, I think this PR is ready to be merged! (cc @vishal-ph )

[vishal-ph]

Ok! Besides the potential issue regarding the Pauli op error, I think this PR is ready to be merged! (cc @vishal-ph )

I see, there are still some changes requested by Shahidee. Are those already implemented? If yes, lets resolve the comments and we can proceed with merge

[EmilianoG-byte]

Ok! Besides the potential issue regarding the Pauli op error, I think this PR is ready to be merged! (cc @vishal-ph )

I see, there are still some changes requested by Shahidee. Are those already implemented? If yes, lets resolve the comments and we can proceed with merge

You man regarding the use of plt.show(), right? With my version of Matplotlib it is not necessary. I am unsure what version is Shahidee using