dm_control: Import of refs/pull/371/head

PiperOrigin-RevId: 507526433
Change-Id: I5557b6ba05664a350746b58a166a2c03f3731b1d

Author: copybara-github

dm_control/manipulation/lift.py

@@ -67,7 +67,7 @@ def _add_vertex_sites(self, box_geom_or_site):
     """Add sites corresponding to the vertices of a box geom or site."""
     offsets = (
         (-half_length, half_length) for half_length in box_geom_or_site.size)
-    site_positions = np.vstack(itertools.product(*offsets))
+    site_positions = np.vstack(list(itertools.product(*offsets)))
     if box_geom_or_site.pos is not None:
       site_positions += box_geom_or_site.pos
     self._vertices = []