View Source BlueHeron.ATT.ReadByGroupTypeRequest (blue_heron v0.5.4)
The ATT_READ_BY_GROUP_TYPE_REQ PDU is used to obtain the values of attributes where the attribute type is known, the type of a grouping attribute as defined by a higher layer specification, but the handle is not known.
Bluetooth Spec v5.2, vol 3, Part F, 3.4.4.9