@@ -10,11 +10,11 @@ import numpy as np

 from scipy.linalg import norm

 from sortedcontainers import SortedSet

-from ..notebook_integration import ensure_holoviews

 from .base_learner import BaseLearner

 from .integrator_coeffs import (b_def, T_left, T_right, ns, hint,

                                 ndiv_max, min_sep, eps, xi, V_inv,

                                 Vcond, alpha, gamma)

+from ..notebook_integration import ensure_holoviews

 def _downdate(c, nans, depth):

@@ -414,7 +414,10 @@ class IntegratorLearner(BaseLearner):

                 self._stack.append(x)

         self.ivals.add(ival)

-    def ask(self, n):

+    def ask(self, n, add_data=True):

+        if not add_data:

+            raise NotImplementedError(

+                "Asking points irreversibly changes the learner's data structure.")

         points, loss_improvements = self.pop_from_stack(n)

         n_left = n - len(points)

         while n_left > 0: