Fix bug with Multitask DeepGP predictive variances. #2123
Merged
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The latent variances of multitask DeepGP models are stored in non-interleaved covariance matrices.
Previously, the MultitaskMultivariateNormal.marginal method implicitly assumed that the function
covariance matrices were interleaved.
In particular, this affects multitask DeepGP models which use a
non-interleaved latent covariance matrix.
With this PR, MultitaskMultivariateNormal.marginal now checks if the input covariance matrix is
interleaved, and makes sure that the returned predictive covariance matrix matches the
interleaved/non-interleaved pattern of the latent covariance matrix.
[Fixes #2702]