code: def concatenate(self, tpl, axis=None):
          
          if axis is None:
              raise NotImplementedError(
                  'Sparse tensor concatenation without axis argument is not supported'
              )
          T = self
          for i in range(1, len(tpl)):
              T = _single_concatenate(T, tpl[i], axis=axis)
          return T
docs: Concatenates sparse tensors.
  
          Parameters
          ----------
          tpl :  tuple of sparse tensors
              Tensors to be concatenated.
          axis :  int, optional
              Axis along which concatenation should take place