code: def dropna_columns(data: pd.DataFrame, max_na_values: int=0.15):
      
      size = data.shape[0]
      df_na = (data.isnull().sum()/size) >= max_na_values
      data.drop(df_na[df_na].index, axis=1, inplace=True)
docs: Remove columns with more NA values than threshold level
  
      :param data:
      :param max_na_values: proportion threshold of max na values
      :return: