code: def axis(self):
      return self._axis
  
file_path: mars/mars/tensor/merge/stack.py
imports: import itertools
  import numpy
  from ...None import opcodes
  from ...serialization.serializables import Int32Field
  from ...utils import has_unknown_shape
  from ..utils import unify_chunks, check_out_param
  from ..array_utils import as_same_device, device
  from ..operands import TensorOperand, TensorOperandMixin
  from ..datasource import tensor
  from ..core import Tensor, TensorOrder
label_desc: Use image node_id 2 for calling the TensorStack obj's underlying member method code with example usage: obj.axis() and returns: self