code: def change_column_if_table_exists(self,
                                        tablename: str,
                                        oldfieldname: str,
                                        newfieldname: str,
                                        newdef: str) -> Optional[int]:
          
          if not self.table_exists(tablename):
              return None
          if not self.column_exists(tablename, oldfieldname):
              return None
          sql = "ALTER TABLE {t} CHANGE COLUMN {old} {new} {newdef}".format(
              t=tablename,
              old=oldfieldname,
              new=newfieldname,
              newdef=newdef,
          )
          log.info(sql)
          return self.db_exec_literal(sql)
docs: Renames a column and alters its definition.