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matplotlib.axes.Axes.minorticks_on
Axes.minorticks_on(self)- 
    
Display minor ticks on the axes.
Displaying minor ticks may reduce performance; you may turn them off using
minorticks_off()if drawing speed is a problem. 
Examples using matplotlib.axes.Axes.minorticks_on
  
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 https://matplotlib.org/3.2.2/api/_as_gen/matplotlib.axes.Axes.minorticks_on.html