Internet Offer Format 3.0 (https://www.idosell.com/pl/shop/developers/formats/iof/internet-offer-format-iof).
Describes the light.xml file.
Holds information about sizes group tree.
Each size group holds one or more sizes.
Each product is associated with a size by sizes.group.size@id attribute.
@id can be passed as a string, but must be unique in its scope and only a-z,A-Z,_,- range chars can be used (e.g. no blanks/spaces allowed)
Format: IOF
IOF version: major.minor
Language: language code in the ISO 639 standard
Date generated: YYYY-MM-DD 00:00:00
All sizes must be hold in given "group" tag
Holds information about a single size.