code: def _get_th2o(self):
      return (
          np.exp(-self._G_H2O * self._ah2o) if self._ah2o != 0 else 1.0
      )
  
imports: from __future__ import annotations
  import logging
  from typing import Optional, Type, Union
  import dask.array
  import numpy
  import xarray
  from satpy.dataset.dataid import WavelengthRange
label_desc: Use image node_id 4 for calling the _ABIAtmosphereVariables obj's underlying member method code with example usage: obj._get_th2o() and returns: unknown