Pip install not working

[Josef-Friedrich]

pip3 install argdown

python3:

>>> import argdown

Python 3.6.5 (default, Apr  1 2018, 05:46:30) 
[GCC 7.3.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import argdown
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.6/dist-packages/argdown/__init__.py", line 1, in <module>
    from argdown.argdown import *
  File "/usr/local/lib/python3.6/dist-packages/argdown/argdown.py", line 272
    if os.is_file('.argdown')
                            ^
SyntaxError: invalid syntax