docs: def enrich(self, column):
          """ This enricher returns the same dataframe
          with a new column named 'domain'.
          That column is the result of splitting the
          email address of another column. If there is
          not a proper email address an 'unknown'
          domain is returned.
  
          :param column: column where the text to analyze is found
          :type data: string
          """
  
          if column not in self.data.columns:
              return self.data
  
          self.data['domain'] = self.data[column].apply(lambda x: self.__parse_email(x))
          return self.data