Adding contrast_sensitivity notebook

[Jackie-Brown]

Adding notebook and supporting files; updating toc.yml, README, and gitignore

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[Jackie-Brown]

@haticekaratay I'm getting a strange PEP8 error when comparing function keywords to None. If I use keyword == None, the checker raises and error and says I should use keyword is None. But if I use keyword is None, I get both a warning in the notebook itself and in the PEP8 checker saying I should use keyword == None. Do you have any ideas on how to get around this?

[gibsongreen]

Everything looks good on the technical side from me with all tests passing, cheers!

[gibsongreen]

@haticekaratay I'm getting a strange PEP8 error when comparing function keywords to None. If I use keyword == None, the checker raises and error and says I should use keyword is None. But if I use keyword is None, I get both a warning in the notebook itself and in the PEP8 checker saying I should use keyword == None. Do you have any ideas on how to get around this?

@Jackie-Brown Hey there! The conditions that I saw with the styling were using string literals to test against None. The string literal in the case of 'keyword' will always pass as True since there is at least one character. Instead of using the string literal I used the function parameter for keyword and that then requires the 'is None' instead of '== None'.