presto-main/src/main/java/io/prestosql/metadata/FunctionId.java/FunctionId/FunctionId
class FunctionId:    @JsonCreator
    public FunctionId(String id)
    {
        requireNonNull(id, "id is null");
        checkArgument(!id.isEmpty(), "id must not be empty");
        checkArgument(id.toLowerCase(Locale.US).equals(id), "id must be lowercase");
        checkArgument(!id.contains("@"), "id must not contain '@'");
        this.id = id;
    }