Error running main.py

[jplegat]

When running main.py, the following error is returned:

Traceback (most recent call last):
  File "main.py", line 43, in <module>
    manager.run()
  File "/Users/xxxx/Desktop/TMOP/tm_manager.py", line 334, in run
    from abstract_filter import TU
  File "/Users/xxxx/Desktop/TMOP/filters/abstract_filter.py", line 56, in <module>
    class AbstractFilter(ABC):
NameError: name 'ABC' is not defined

Running python 2.7.18