Pandas groupby two columns and plot

I have a dataframe like this:

import numpy as npimport pandas as pdimport matplotlib.pyplot as plt%matplotlib inlinedf = pd.DataFrame({'category': list('XYZXY'), 'B': range(5,10),'sex': list('mfmff')})

I want to plot count of sex male or female based on category from column 'category'.

I tried:
df.groupby(['category','sex'])['category','sex'].count().plot.bar()

But this gives:
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How do I get the count of sex per category?