protected String consumeLabel() {
            if (consumeOptional('\'')) {
                int endQuote = string.indexOf('\'', position);
                if (endQuote < 0)
                    throw new IllegalArgumentException("At value position " + position +
                                                       ": A label quoted by a tick (') must end by another tick");
                String label = string.substring(position, endQuote);
                position = endQuote + 1;
                return label;
            }
            else if (consumeOptional('"')) {
                int endQuote = string.indexOf('"', position);
                if (endQuote < 0)
                    throw new IllegalArgumentException("At value position " + position +
                                                       ": A label quoted by a double quote (\") must end by another double quote");
                String label = string.substring(position, endQuote);
                position = endQuote + 1;
                return label;
            }
            else {
                return consumeIdentifier();
            }
        }
Derives the tensor type from the first address string in the given tensor string
vespajlib/src/main/java/com/yahoo/tensor/TensorParser.java