The minimal code that would cause an unexpected KeyError in TF2.0

tf_keyerror.py

import tensorflow as tf #tf2.0
from collections import OrderedDict

class MyNamedTuple(OrderedDict):
    def __iter__(self):  # iterate over values to unpack, e.g., arg1, arg2, arg3 = MyNamedTuple(...)
        for v in self.values():
            yield v
          
class MyModule(tf.Module):
    def __call__(self):
        self.module = MyNamedTuple({'arg': 'hello'}) # cause KeyError
        self.v = tf.Variable([1, 2, 3]) # some variables
        
module = MyModule('my_module')
module()
print(module.variables) #KeyError