presto-main/src/main/java/io/prestosql/metadata/Signature.java/Signature/toString
class Signature:    @Override
    public String toString()
    {
        List<String> allConstraints = concat(
                typeVariableConstraints.stream().map(TypeVariableConstraint::toString),
                longVariableConstraints.stream().map(LongVariableConstraint::toString))
                .collect(Collectors.toList());

        return name + (allConstraints.isEmpty() ? "" : "<" + Joiner.on(",").join(allConstraints) + ">") + "(" + Joiner.on(",").join(argumentTypes) + "):" + returnType;
    }