Jorn Hoofwijk
--- a/adaptive/learner/triangulation.py
+++ b/adaptive/learner/triangulation.py
        """Simplices originating from a vertex don't overlap."""
        raise NotImplementedError

+    def get_neighbours_from_vertices(self, simplex):
--- a/adaptive/learner/learnerND.py
+++ b/adaptive/learner/learnerND.py
+        at the boundary.
+
+    Returns
+    -------
+    loss : float
+    """
+
+    neighbors = [n for n in neighbors if n is not None]
+    if len(neighbors) == 0:
+        return 0
+
+    return sum(simplex_volume_in_embedding([*simplex, neighbour])
+               for neighbour in neighbors) / len(neighbors)
+
+def get_curvature_loss(curvature_factor=1, volume_factor=0, input_volume_factor=0.05):
+    # XXX: add doc-string!