code: def modify_column_if_table_exists(self,
                                        tablename: str,
                                        fieldname: str,
                                        newdef: str) -> Optional[int]:
          
          if not self.table_exists(tablename):
              return None
          sql = "ALTER TABLE {t} MODIFY COLUMN {field} {newdef}".format(
              t=tablename,
              field=fieldname,
              newdef=newdef
          )
          log.info(sql)
          return self.db_exec_literal(sql)
docs: Alters a column's definition without renaming it.