Overrides the default structure constructor so a schema can be built in one expression (my_maml = parquet_schema(table="my_table")) as an alternative to call my_maml%init(table="my_table"); both call parquet_schema_new/schema_init under the hood. table is the only required argument (the MAML table: key); survey, dataset, version, date, author, description, license, and maml_version are all optional and set the correspondingly-named MAML header key when given. Returns the newly initialized schema.