steal_history in explicable

pymath/calculus/explicable.py

@@ -128,6 +128,18 @@ class Explicable(Renderable):
         """
         self.steps = steps + self.steps
 
+    def steal_history(self, arg1):
+        """ Steal the history of arg1 for itself
+
+        :param arg1: a potential Explicable
+
+        """
+        try:
+            self.this_append_before(list(arg1.explain()))
+        except AttributeError:
+            pass
+
+
     @staticmethod
     def merge_history(explicables):
         r""" Take a list of Explicable objects, explain where they are from and merge their history