presto-accumulo/src/main/java/io/prestosql/plugin/accumulo/conf/AccumuloTableProperties.java/AccumuloTableProperties/getColumnMapping
class AccumuloTableProperties:    public static Optional<Map<String, Pair<String, String>>> getColumnMapping(
            Map<String, Object> tableProperties)
    {
        requireNonNull(tableProperties);

        @SuppressWarnings("unchecked")
        String strMapping = (String) tableProperties.get(COLUMN_MAPPING);
        if (strMapping == null) {
            return Optional.empty();
        }

        // Parse out the column mapping
        // This is a comma-delimited list of "(presto, column:accumulo, fam:accumulo qualifier)" triplets
        ImmutableMap.Builder<String, Pair<String, String>> mapping = ImmutableMap.builder();
        for (String m : COMMA_SPLITTER.split(strMapping)) {
            String[] tokens = Iterables.toArray(COLON_SPLITTER.split(m), String.class);
            checkState(tokens.length == 3, "Mapping of %s contains %s tokens instead of 3", m, tokens.length);
            mapping.put(tokens[0], Pair.of(tokens[1], tokens[2]));
        }

        return Optional.of(mapping.build());
    }