Extract tf.function decorator arguments

[tatianacv]

Currently, we are not dealing with tf.function decorator parameter values, just with the existence of those parameters.

Do we need dataflow or does parsing literals enough? How often are variables used to decorator arguments? Can we tell when variables are used? If we go only with literals, can we throw an exception when a variable is used so that we know how many times this happens. Better yet, we can "fail" the function by adding a precondition failure to the function. In other words, if we can't exact the decorator argument, chances are we won't be able to get a good handle on the function's status.

[khatchad]

tf.function parameter values sounds ambigious because when a function is transformed to a tf.function, we typically cal that a tf.function. So, which parameters are we approximating, the one from the function or the one from the decorator? Both may have parameters.

[tatianacv]

Understood, thanks. Yeah, I updated that to make it more clear in the description. I believe we will need information both on the function and on the decorator, but this issue is related to the decorator's parameter values.

[khatchad]

parameter values = arguments (title simplification)

[khatchad]

Isn't this the same as #111?

[tatianacv]

Yes, it seems that way.

[khatchad]

Dupe of #111.