Remove use of eval() from operators.py

[panzi]

Use np.float32() instead.

What problem does this PR solve?

Using eval() can lead to code injections.

I think eval() is only used to parse a floating point number here. This change preserves the correct behavior if the string "None" is supplied. But if that behavior isn't intended then this part could be just deleted instead, since np.float32() is parsing strings anyway:

        if isinstance(scale, str):
            scale = eval(scale)

Type of change

• Bug Fix (non-breaking change which fixes an issue)