add itertools.chain.from_iterable

Author: timfel

graalpython/lib-graalpython/itertools.py

@@ -62,9 +62,15 @@ def __next__(self):
             return next(self._current)
         except (StopIteration, IndexError):
             self._idx += 1
+            if self._idx >= self._len:
+                raise StopIteration
             self._current = iter(self._iterables[self._idx])
             return self.__next__()
 
+    @classmethod
+    def from_iterable(cls, arg):
+        return cls(*iter(arg))
+
 
 class starmap():
     pass