PairwiseDistance fit_transform method returns a non-symmetric matrix

[tennets]

Hi Everyone 😄,

I am very new to TDA in general, and giotto-tda in particular so I am very grateful for your work.
I appreciate any help you can provide.

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Background

After generating the persistence diagrams, I use the fit_transform method from the PairwiseDistance class in the diagram module to compute the distance matrix (according to either "Bottleneck" or "Wasserstein" metric).

However, I get an almost symmetric matrix, like this one:

[[0.         1.50765398 1.13865528 0.92542782]
 [1.50774904 0.         2.19319229 1.96137276]
 [1.13860347 2.19324773 0.         0.59201808]
 [0.92544839 1.9613611  0.59200822 0.        ]]

This gives me trouble, as the next step in my pipeline is visualising the diagrams using the distance matrix.
To do that, I use Muli Dimensional Scaling (MDS) (I use the MDS class in Sklear) which requires symmetric distance matrices.

Questions

1. By reading the docs to me is not clear, but why fit_transform does not return a symmetric matrix and it is possible ensure it does?
2. If it is not possible, do you have any suggestion on how I could visualise the diagrams as 2d points like I would with MDS?

Thanks!