docstr: Compute the arithmetic mean along the specified axis.
  
  Args:
      axis (int or ``None``): Axis along which the sum is computed.
          If it is ``None``, it computes the average of all the elements.
          Select from ``{None, 0, 1, -2, -1}``.
  
  Returns:
      cupy.ndarray: Summed array.
  
  .. seealso::
     :meth:`scipy.sparse.spmatrix.mean`
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code: def mean(self, axis=None, dtype=None, out=None):
      """Compute the arithmetic mean along the specified axis.
  
      Args:
          axis (int or ``None``): Axis along which the sum is computed.
              If it is ``None``, it computes the average of all the elements.
              Select from ``{None, 0, 1, -2, -1}``.
  
      Returns:
          cupy.ndarray: Summed array.
  
      .. seealso::
         :meth:`scipy.sparse.spmatrix.mean`
  
      """
      _sputils.validateaxis(axis)
      nRow, nCol = self.shape
      data = self.data.copy()
  
      if axis is None:
          n = nRow * nCol
      elif axis in (0, -2):
          n = nRow
      else:
          n = nCol
  
      return self._with_data(data / n).sum(axis, dtype, out)
  
imports: import cupy
  import numpy
  from cupy._core import internal
  from cupy import _util
  from cupyx.scipy.sparse import _base
  from cupyx.scipy.sparse import _coo
  from cupyx.scipy.sparse import _sputils
label_desc: Use image node_id 10 for calling the _data_matrix obj's underlying member method code with example usage: obj.mean(axis, dtype, out) and returns: self