Currently code like this is repeated several times:

field = mapping.STORAGE_TENSOR_TYPE_TO_FIELD[
    mapping.TENSOR_TYPE_TO_STORAGE_TENSOR_TYPE[data_type]]
getattr(tensor, field)

This is repetitive and can be encapsulated in a helper function.
Also the name "storage tensor type" is misleading and has led to at least one bug.

We should:

1. Add a function that does all this
2. Deprecate mapping.STORAGE_TENSOR_TYPE_TO_FIELD and mapping.TENSOR_TYPE_TO_STORAGE_TENSOR_TYPE. Ideally log a warning when they're accessed.
3. Eventually, then in the next release, remove those fields entirely.