This function constructs a likelihood object to represent a negative Binomial likelihood node.

## Arguments

- input_dim
a vector of length two that contains the indices of two GP nodes in the feeding layer whose outputs feed into this likelihood node. When set to

`NULL`

, all outputs from GP nodes in the feeding layer feed into this likelihood node, and in such a case one needs to ensure that only two GP nodes are specified in the feeding layer. Defaults to`NULL`

.

## Details

See further examples and tutorials at https://mingdeyu.github.io/dgpsi-R/.