This structure contains UDF parent's mapping data information:

num_mapping_objs: At the instantiation, this number of mapping objects
can be obtained by calling the public API routine
UF_MODL_init_udf_insert_data_from_def(). At the editing,
it can be obtained by calling the public API routine
UF_MODL_ask_instantiated_udf().

reverse_objs_dir: must be inputted by the user for both of instantiation
and editing.

For the UDF parent's types: Edges, Curves, Points. There is no need to
prepare the mapping data.

For the UDF parent's types: Faces, Bodies, Sketches, Feature curves and
output objects of Smart Collectors. If there is a need to do the mapping
at the instantiation or editing, then use these 2 arrays: old_output_objs[]
and new_output_objs[] to store the objects that need to be mapped:

At the instantiation, the array old_output_objs[] can be obtained
(i.e. memory allocation and content) from the UDF feature definition by
calling the public API routine UF_MODL_init_udf_insert_data_from_def().
The memory of array new_output_objs[] must be allocated by the user and
its content must be also inputted by the user.

At the editing, the array old_output_objs[] can be obtained (i.e. memory
allocation and content) from the UF_MODL_ask_instantiated_udf(). The memory
of array new_output_objs[] must be allocated by the user and its content
must be also inputted by the user.

For the UDF parent's types: Output curves of Smart Sections. The user has to
prepare the mapping data. If there is a need to do the mapping at the
instantiation or editing, then use these 2 arrays: old_output_objs_index[]
and new_output_objs_index[] to store the Smart Section's output objects
that need to be mapped. Note that these output objects are condemned, which
are not displayed (i.e., invisible). They can't be used or destroyed for
further applications:

At the instantiation, the array old_output_objs_index[] can be obtained
(i.e. memory allocation and content) from the UDF feature definition by
calling the public API routine UF_MODL_init_udf_insert_data_from_def().
The memory of array new_output_objs_index[] must be allocated by the user
and its content must be also inputted by the user.

At the editing, the array old_output_objs_index[] can be obtained (i.e. memory
allocation and content) from the UF_MODL_ask_instantiated_udf(). The memory of
array new_output_objs_index[] must be allocated by the user and its content
must be also inputted by the user.