text: # missing values
  
  # load libraries
  import missingno as msno
  import matplotlib.pyplot as plt
  
  train_df.isnull().sum()[train_df.isnull().sum() > 0]
  # output of these - columns, are fed to msno matrix
  
  msno.matrix(train_df[['v2a1', 'v18q1', 'rez_esc', 'meaneduc', 'SQBmeaned']], color = (0.211, 0.215, 0.274))
  
  plt.show()
  