function isAxisUsedInTheGrid(axisModel, gridModel, ecModel) {
	        return axisModel.getCoordSysModel() === gridModel;
	    }
Usage:
     grid.getCartesian(xAxisIndex, yAxisIndex);
     grid.getCartesian(xAxisIndex);
     grid.getCartesian(null, yAxisIndex);
     grid.getCartesian({xAxisIndex: ..., yAxisIndex: ...});

@param {number|Object} [xAxisIndex]
@param {number} [yAxisIndex]