code: func (p *MySQLPrivilege) FindRole(user string, host string, role *auth.RoleIdentity) bool {
  	rec := p.matchUser(user, host)
  	r := p.matchUser(role.Username, role.Hostname)
  	if rec != nil && r != nil {
  		key := rec.User + "@" + rec.Host
  		return p.RoleGraph[key].Find(role.Username, role.Hostname)
  	}
  	return false
  }
docs: // FindRole is used to detect whether there is edges between users and roles.