def make_node(self, *mat):
        if not mat:
            raise ValueError('Cannot join an empty list of sparses.')
        var = [as_sparse_variable(x) for x in mat]

        for x in var:
            assert x.format != ["csr", "csc"]

        return gof.Apply(self,
                         var,
                         [SparseType(dtype=self.dtype,
                                     format=self.format)()])
dataset/ETHPy150Open rizar/attention-lvcsr/libs/Theano/theano/sparse/basic.py/HStack.make_node/operator `in` -> `!=`