This is a good example of inplace not working as-expected

good_example_of_fillna_inplace_not_working.py

df = pd.DataFrame(
	{'Label': [np.nan, np.nan, 'Label1', 'Label2'],
	 'URL': ['https://www.website.com/where-to-buy',
		 np.nan, np.nan, 'https://www.website.com/store']
	 }, columns=['Label', 'URL'])

# this does not actually replace inplace!
df[['Label', 'URL']].fillna('', inplace=True)

# you have to assign it or use a dict
self.data.fillna({'Campaign': '', 'Final URL': ''}, inplace=True)

# or
df[['Label', 'URL']] = df[['Label', 'URL']].fillna('')