Add tests for negative numbers in utils

[MasterAffan]

File:
tests/test_utils.py

Add comprehensive tests for is_number in tests/test_utils.py, covering:

1.Positive integers
2.Negative integers
3.Floats

[garje-vaishnavi]

@MasterAffan Assign this issue to me

[MasterAffan]

@garje-vaishnavi assigned

[MasterAffan]

@garje-vaishnavi were you able to solve this issue, if yes please make a pull request