presto-main/src/main/java/io/prestosql/util/JsonUtil.java/BooleanBlockBuilderAppender/append
class BooleanBlockBuilderAppender:        @Override
        public void append(JsonParser parser, BlockBuilder blockBuilder)
                throws IOException
        {
            Boolean result = currentTokenAsBoolean(parser);
            if (result == null) {
                blockBuilder.appendNull();
            }
            else {
                BOOLEAN.writeBoolean(blockBuilder, result);
            }
        }