code: func (s *session) StmtGetMutation(tableID int64) *binlog.TableMutation {
  	st := &s.txn
  	if _, ok := st.mutations[tableID]; !ok {
  		st.mutations[tableID] = &binlog.TableMutation{TableId: tableID}
  	}
  	return st.mutations[tableID]
  }
docs: // StmtGetMutation implements the sessionctx.Context interface.