Calling mpl_set_num_internal_nodes(n, morphy) ADDS n to the number of internal nodes
mpl_set_num_internal_nodes(10, morphy)
mpl_set_num_internal_nodes(20, morphy)
mpl_set_num_internal_nodes(10, morphy)
mpl_get_num_internal_nodes(morphy) // returns 40, expected 10
Calling mpl_set_num_internal_nodes(n, morphy) ADDS n to the number of internal nodes