lib/tensor_stream/ops.rb
def stack(values, axis: 0, name: "stack")
      _op(:stack, *values, axis: axis, name: name)
    end
def stack(values, axis: 0, name: "stack")
      _op(:stack, *values, axis: axis, name: name)
    end
Stacks a list of rank-R tensors into one rank-(R+1) tensor.