udim commented on a change in pull request #13493:
URL: https://github.com/apache/beam/pull/13493#discussion_r538762100
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File path: sdks/python/apache_beam/typehints/sharded_key_type.py
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@@ -25,8 +25,12 @@
from apache_beam.typehints.typehints import match_type_variables
from apache_beam.utils.sharded_key import ShardedKey
+from future.utils import with_metaclass
-class ShardedKeyTypeConstraint(typehints.TypeConstraint):
+
+class ShardedKeyTypeConstraint(with_metaclass(typehints.GetitemConstructor,
Review comment:
This works:
```py
def __class_getitem__(cls, py_type):
return cls(py_type)
```
The alternative is to use a wrapper object instance such as `IterableHint`
that has `__getitem__`, and then define `Iterable = IterableHint()`.
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