I can’t change the size of a picture - Matplotlib

Question

I need to create a figure in bars, I’m trying to increase the size, as follows:

plt.figure(figsize=(8,8))
plt.bar(df_nacoes_ano)
plt.show()

But I get the following message:

TypeError: bar() missing 1 required positional argument: 'height'

I tried to insert the height but I have not yet succeeded in increasing the figure.

What can I do??