time_value not available in Python Calculator

It appears that time_value, which is supposed to resolve to the current time, is not always available in the Python Calculator. To replicate the issue, do the following:

1. Create a Wavelet source. Apply.
2. Create a Python Calculator. Set the expression to RTData * time_value. Apply.

You will get a Python error about the * operator not valid for float and NullType. This is because time_value is not defined.

I suspect the problem is that the Python Calculator is trying to get the time value from the input object, and the input object is not a temporal object so has no time value. But it is really useful to use the pipeline time with the Python Calculator on a non-temporal object to quickly turn it into a temporal object.