Example code fails in python 3.6

[exit99]

class Accounts(testdata.DictFactory):
    id = testdata.CountingFactory(10)
    first = testdata.FakeDataFactory('firstName')
    last = testdata.FakeDataFactory('lastName')
    address = testdata.FakeDataFactory('address')
    age = testdata.RandomInteger(10, 30)

Accounts().generate(10)

raises this exception:

tdata/dictionary.py", line 27, in __init__
    self._child_factories = deepcopy(self._child_factory_tree)
AttributeError: 'Accounts' object has no attribute '_child_factory_tree'

[jjpazos]

No errors with Python 2.7

[gudata]

Errors on python 3.8.2