Every Player may have BodyParts if it so chooses. In the PlayerClass, they are defined as:
pub struct BodyPart {
pub index: u16,
pub body_part: String,
pub total_item_spots: Option<u64>,
pub inherited: InheritanceState,
On the actual Player there is no corresponding state, as the only stateful part of a BodyPart is what is equipped on it, and this is contained in the equipped_items array. You'll notice that each BodyPart has its own index - this, like BasicStats, is a required unique field, to help disambiguate parts.
It's possible for a BodyPart to equip more than one item (see total_item_spots).