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 \((b \times n \times m)\) tensor, batch2 is a
\((b \times m \times p)\) tensor, then input must be
broadcastable  with a
\((b \times n \times p)\) tensor and out will be a
\((b \times n \times p)\) tensor. Both alpha and beta mean the
same as the scaling factors used in torch_addbmm.
$$
    \mbox{out}_i = \beta\ \mbox{input}_i + \alpha\ (\mbox{batch1}_i \mathbin{@} \mbox{batch2}_i)
$$
For inputs of type FloatTensor or DoubleTensor, arguments beta and
alpha must be real numbers, otherwise they should be integers.