PK_ERROR_code_t     PK_ASSEMBLY_ask_parts_transfs
(
--- received arguments ---
PK_ASSEMBLY_t       assembly,  --- assembly

--- returned arguments ---
int          *const n_parts,   --- number of parts in assembly (>=0)
PK_PART_t   **const parts,     --- parts in assembly (optional)
PK_TRANSF_t **const transfs    --- transforms in assembly (optional)
                               ---     (may be PK_ENTITY_null)
)


This function returns the parts in an assembly, together with their associated
transforms. As each part corresponds to one instance, there may be duplicates
in the parts array.


The transforms are the transforms of the instances in the assembly, not copies
of them. Some or all of them may be PK_ENTITY_null.

The output array parts is optional.  If it is set to NULL, the function will
not compute the parts array.

The output array transfs is optional.  If it is set to NULL, the function
will not compute the transfs array.