code: def is_erroneous(self, field, sources):
          
          if self._KEYS.ERRORS in self:
              my_errors = self[self._KEYS.ERRORS]
              for alias in sources.split(','):
                  source = self.get_source_by_alias(alias)
                  bib_err_values = [
                      err[ERROR.VALUE] for err in my_errors
                      if err[ERROR.KIND] == SOURCE.BIBCODE and
                      err[ERROR.EXTRA] == field
                  ]
                  if (SOURCE.BIBCODE in source and
                          source[SOURCE.BIBCODE] in bib_err_values):
                      return True
  
                  name_err_values = [
                      err[ERROR.VALUE] for err in my_errors
                      if err[ERROR.KIND] == SOURCE.NAME and err[ERROR.EXTRA] ==
                      field
                  ]
                  if (SOURCE.NAME in source and
                          source[SOURCE.NAME] in name_err_values):
                      return True
  
          return False
docs: Check if attribute has been marked as being erroneous.