Notes on metrics' symmetry

[snk4tr]

Is your feature request related to a problem? Please describe.
Currently, it is not clear which metrics are symmetric and which are not. It may cause potential low reproducibility of reported metrics scores. The process of debugging such problems may be tedious and time consuming.

Describe the solution you'd like
All metrics have to include a note in the docstring on their symmetry. Moreover, it might make sense to add a warning for asymmetric metrics that would trigger every time a metric is run. @denproc @zakajd please comment on that.

Additional context
For PieAPP:
metric(distorted, reference) - 0.836
metric(reference, distorted) - 0.601

[denproc]

Hi @snk4tr,
In general, our documentation explaines the inputs of the metrics and classes as input tensor and target tensor. Therefore, a user could simpy follow the explanation or use key words to provide arguments to avoid wrong results.

In my mind, adding a note to assymetric measures is a great suggestion to make the property more visible. As we improve the metric description, it is related to #318.

On the other hand, I would avoid adding proposed warning to the metrics. In this case, we have no additional information to warn user about potential errors due to our code, dependencies or sudden change of interface with a new release. The proper use of the metric is up to user and their ability to read the documentation.

[zakajd]

Agree with Denis.
Clearly stating the order of input and target tensors in documentation is important. Warning could become too annoying, so don't see this necessary.