An imported CAD file: its bodies, each with its faces and edges.
The part's solid bodies, in a stable order sorted by their bounding boxes. A surface the file holds without a solid is not a body: find its faces under Faces.
The faces of the part's surfaces — every shell or face the file holds without a solid, such as a surface saved as STEP. Pick one as a CAD Face; a solid body's faces are under its own Faces.
The box that encloses every body of the part.
The part's name, if the STEP file gave it one.