Testing for the _is_smiles positive test when Chem is None

[Faith-Adegoke]

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
The task is to test the CompoundIdentifier class (specifically the _is_smiles function) in ersilia/utils/identifiers/compound.py.

Changes to be made

• Create a new Python file under the 'test' folder.
• Use the pytest framework to implement unit testing for the _is_smiles positive test when Chem is None.
• Give a correct SMILES string for testing (I used Dimethyl ether SMILES representation (COC)).
• Verify that the function returns a true value when the right string is passed.

Status

The test has been implemented and it passed. This is the screenshot.

To do

• To be reviewed by mentor.

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

Related to #1319

[DhanshreeA]

Closing as standard not adhered to, and we already have a test for this implemented in #1332