title: python 3.5 in statsmodels ImportError: cannot import name '_representation'
body: <p>I cannot manage to import statsmodels.api correctly when i do that I have this error:</p>
  
  <blockquote>
    <p>File "/home/mlv/.local/lib/python3.5/site-packages/statsmodels/tsa/statespace/tools.py", line 59, in set_mode
        from . import (_representation, _kalman_filter, _kalman_smoother,
    ImportError: cannot import name '_representation'</p>
  </blockquote>
  
  <p>I already try to re-install or update it, that does not change.
  plese i need help =) </p>