ok i may have figured it out...

code-experiments/build/python/src/cocoex/function.pyx

@@ -22,8 +22,7 @@ cdef extern from 'coco.h':
 # add a declaration to the generated source files.
 cdef extern coco_problem_t *coco_get_bbob_problem(size_t function, size_t
                                                   dimension, size_t instance)
-cdef extern double coco_problem_get_best_value(coco_problem_t *p)
-
+
 cdef class BenchmarkFunction:
     """A bare benchmark function from one of the available suites.
 
@@ -103,12 +102,7 @@ cdef class BenchmarkFunction:
     def __del__(self):
         if self._problem != NULL:
             coco_problem_free(self._problem)
-
-
-    def best_value(self):
-        """Return the best (lowest) possible function value"""
-        return coco_problem_get_best_value(self._problem)
-
+
     def __str__(self):
         return self.id