docs: def enrich(self, columns):
          """ This method convert to utf-8 the provided columns
  
          :param columns: list of columns to convert to
          :type columns: list of strings
          :return: original dataframe with converted strings
          :rtype: pandas.DataFrame
          """
  
          for column in columns:
              if column not in self.data.columns:
                  return self.data
  
          for column in columns:
              a = self.data[column].apply(self.__remove_surrogates)
              self.data[column] = a
  
          return self.data