separation of concerns to support targeted override in peppy; pepkit/…

…peppy#262

attmap/_att_map_like.py

@@ -103,13 +103,17 @@ def add_entries(self, entries):
         except AttributeError:
             entries_iter = entries
         for k, v in entries_iter:
-            if k not in self or not (isinstance(v, Mapping) and
-                                     isinstance(self[k], AttMapLike)):
+            if self._ready_to_store(k, v):
                 self.__setitem__(k, v)
             else:
                 self[k].add_entries(v)
         return self
 
+    def _ready_to_store(self, k, v):
+        """ Determine whether given KV pair is ready to be stored. """
+        return k not in self or not \
+            (isinstance(v, Mapping) and isinstance(self[k], AttMapLike))
+
     def is_null(self, item):
         """
         Conjunction of presence in underlying mapping and value being None