PK_ERROR_code_t    PK_BODY_ask_shells
(
--- received arguments ---
PK_BODY_t          body,            --- a body

--- returned arguments ---
int         *const n_shells,        --- number of shells (>= 0)
PK_SHELL_t **const shells           --- shells (optional)
)


This function returns the set of shells in the given body.


The output array shells is optional. If it is set to NULL, the function
will only compute the number of shells in the body.