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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def stack(xs, dim_name, axis=0, name=None):
 """Stack multiple Tensors to make a new dimension. Args: xs: a list of Tensors with identical shapes. dim_name: a string (name of the new dimension) axis: an integer (index of the new dimension in the output shape) name: an optional string Returns: a Tensor """

  ret = StackOperation(xs, dim_name, axis, name).outputs[0]
  return ret