Pubchem smiles to inchikey negative

[olamidepeterojo]

Thank you for taking your time to contribute to Ersilia, just a few checks before we proceed

• Have you followed the guidelines in our Contribution Guide
• Have you written new tests for your core changes, as applicable?
• Have you successfully ran tests with your changes locally?

Description

This commit will add a negative test for _pubchem_smiles_to_inchikey

Changes to be made

Added a new test function for _pubchem_smiles_to_inchikey negative test in test/test_compound_identifier.py

Status

• Written test and validated logically using pytest

To do

If this is a work in progress, Replace this line with your next steps

Is this pull request related to any open issue? If yes, replace issueID below with the issue ID

Related to #1319