Performs a batch matrix-matrix product of matrices in batch1
and batch2. input is added to the final result.
batch1 and batch2 must be 3-D tensors each containing the same number of matrices.
If batch1 is a (b×n×m) tensor, batch2 is a (b×m×p) tensor, then input must be broadcastable with a (b×n×p) tensor and out will be a (b×n×p) tensor. Both alpha and beta mean the same as the scaling factors used in torch_addbmm.