presto-rcfile/src/main/java/io/prestosql/rcfile/RcFileWriteValidation.java/RcFileWriteValidationBuilder/addMetadataProperty
class RcFileWriteValidationBuilder:        public RcFileWriteValidationBuilder addMetadataProperty(String key, String value)
        {
            metadata.put(key, value);
            return this;
        }