Python 是否从xarray.Dataset中删除坐标对象？

我有一个xarray.Dataset，如下图所示。 我想从数据集中删除“空”坐标对象。 我该怎么做？ 附加了一个示例代码（输出与图像略有不同）

ds.sel（MachineID=ds.MachineID！=“Empty”）

应该让您开始学习。

import xarray as xr
import numpy as np
import pandas as pd

x = np.linspace(0,1500,16)
y1 = np.random.random((1,1,1,1,1,1,6,len(x)))
y2 = np.random.random((1,1,1,1,1,1,6,len(x)))
y3 = np.random.random((1,1,1,1,1,1,6,len(x)))
y4 = np.random.random((1,1,1,1,1,1,6,len(x)))

da1 = xr.DataArray(y1, dims=('MachineID','MachineType','Year','Month','Compensation','Axis','SensorID','Pos'),
                       coords={'MachineID':['Empty'],'MachineType':['Empty'],'Year':['Empty'],'Month':['Empty'],'Compensation':[0],
                            'Axis':['Empty'],'SensorID':range(6),'Pos':x},
                       name='val')

da2 = xr.DataArray(y2, dims=('MachineID','MachineType','Year','Month','Compensation','Axis','SensorID','Pos'),
                       coords={'MachineID':['MC_B'],'MachineType':['Car'],'Year':['2020'],'Month':['Aug'],'Compensation':[1],
                            'Axis':['X'],'SensorID':range(6),'Pos':x},
                       name='val')

da3 = xr.DataArray(y3, dims=('MachineID','MachineType','Year','Month','Compensation','Axis','SensorID','Pos'),
                       coords={'MachineID':['MC_C'],'MachineType':['Train'],'Year':['2020'],'Month':['Aug'],'Compensation':[1],
                            'Axis':['X'],'SensorID':range(6),'Pos':x},
                       name='val')

da4 = xr.DataArray(y4, dims=('MachineID','MachineType','Year','Month','Compensation','Axis','SensorID','Pos'),
                       coords={'MachineID':['MC_D'],'MachineType':['Train'],'Year':['2020'],'Month':['Aug'],'Compensation':[1],
                            'Axis':['X'],'SensorID':range(6),'Pos':x},
                       name='val')

#%%
df = pd.concat([da1.to_dataframe(), da2.to_dataframe(), da3.to_dataframe(), da4.to_dataframe()])
ds=xr.Dataset.from_dataframe(df)
ds