input: Write a python function to remove irrelevant columns from a pandas DataFrame.
  assert remove_irrelevant_columns(pd.DataFrame({'plot': ['plot1'], 'cast': ['cast1'], 'director': ['director1'], 'year': [2000], 'other': ['other1']})).columns.tolist() == ['other']
  assert remove_irrelevant_columns(pd.DataFrame({'plot': ['plot2'], 'cast': ['cast2'], 'director': ['director2'], 'year': [2001], 'other1': ['other1'], 'other2': ['other2']})).columns.tolist() == ['other1', 'other2']
  assert remove_irrelevant_columns(pd.DataFrame({'plot': ['plot3'], 'cast': ['cast3'], 'director': ['director3'], 'year': [2002], 'name': ['name1']})).columns.tolist() == ['name']
output: def remove_irrelevant_columns(df):
      irrelevant_columns = ['plot', 'cast', 'director', 'year']
      return df.drop(columns=[col for col in df.columns if col in irrelevant_columns])