removed a singleton comparison pitfall from the code

[NaelsonDouglas]

The problem In Python when comparing a variable to a singleton value like True, False and None it is advised to use the operator 'is' instead of '=='. This pitfall was detected using Pylint, which indicated it under the code C0121, as seen on the link below https://vald-phoenix.github.io/pylint-errors/plerr/errors/basic/C0121.html

The solution Just changed the operator

[NaelsonDouglas]

The same if checks if the data is not None and then checks if its a True boolean, that's why the two checks were left

[anishathalye]

I think this can be changed to just if preserve_colors:

[NaelsonDouglas]

I think this can be changed to just if preserve_colors:

Agree.

Done in https://github.com/anishathalye/neural-style/pull/178/commits/c2f6c4d451aa9eb34f772e21ab1d1385f2629a5d

[anishathalye]

Thanks, rebased and merged!