title: How to get country border lines while plotting with imshow in python
body: <p>I am trying to plot seasonal mean from a netcdf file using xarray and matplotlib. I am getting the plots with latitude and longitude axes but there is no country border line. How to obtain country border lines on the plots. </p>
  
  <pre><code>import xarray as xr
  import matplotlib as mpl
  import matplotlib.pyplot as plt
  
  fname='/home/atmosphere/data/outputs/2010.nc'         #&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;&lt;
  
  ds=xr.open_mfdataset(fname)
  varlist=list(ds.variables)
  imr=ds.sel(lat=slice(0,35),lon=slice(60,100)) #subsetting overthe region
  imrbt=imr['temp']                             #making into a data array  
  ds['time.season']
  
  seasonal=imrbt.groupby('time.season').mean(dim='time')
  seasonal.plot.imshow(col='season',robust=True)
  </code></pre>