presto-spi/src/main/java/io/prestosql/spi/security/RoleGrant.java/RoleGrant/toString
class RoleGrant:    @Override
    public String toString()
    {
        return "RoleGrant{" +
                "grantee=" + grantee +
                ", roleName='" + roleName + '\'' +
                ", grantable=" + grantable +
                '}';
    }