Get flow direction induced cell shift dict.
        Args:
            flow_model: Currently, "TauDEM", "ArcGIS", and "Whitebox" are supported.

def get_cell_shift(flow_model):
        """Get flow direction induced cell shift dict.
        Args:
            flow_model: Currently, "TauDEM", "ArcGIS", and "Whitebox" are supported.
        """
        assert flow_model.lower() in FlowModelConst.d8_deltas
        return FlowModelConst.d8_deltas.get(flow_model.lower())