code: func (p *MySQLPrivilege) LoadRoleGraph(ctx sessionctx.Context) error {
  	p.RoleGraph = make(map[string]roleGraphEdgesTable)
  	err := p.loadTable(ctx, "select FROM_USER, FROM_HOST, TO_USER, TO_HOST from mysql.role_edges;", p.decodeRoleEdgesTable)
  	if err != nil {
  		return errors.Trace(err)
  	}
  	return nil
  }
docs: // LoadRoleGraph loads the mysql.role_edges table from database.