Try to fix mypy

Author: MaximSmolskiy

Diff for: neural_network/input_data.py

@@ -28,7 +28,8 @@
 from tensorflow.python.platform import gfile
 from tensorflow.python.util.deprecation import deprecated
 
-_Datasets = typing.NamedTuple("_Datasets", ["train", "validation", "test"])
+_Datasets = typing.NamedTuple(
+    "_Datasets", [("train", _DataSet), ("validation", _DataSet), ("test", _DataSet)])
 
 # CVDF mirror of http://yann.lecun.com/exdb/mnist/
 DEFAULT_SOURCE_URL = "https://storage.googleapis.com/cvdf-datasets/mnist/"