title: Problem with Tensorflow package when it's used by Lucid package
body: <p>So I am trying to use the code in this link:</p>
  
  <pre><code>https://colab.research.google.com/github/tensorflow/lucid/blob/master/notebooks/differentiable-parameterizations/style_transfer_2d.ipynb#scrollTo=FsFc1mE51tCd
  </code></pre>
  
  <p>it's giving some errors when Lucid is trying to use Tensorflow at the first part where it tries to import. I tried to install some different Tensorflow versions and some different Lucid versions but still could not get it working. </p>
  
  <p>Here are some of errors I get:</p>
  
  <p>when I try</p>
  
  <pre><code>from lucid.modelzoo import vision_models
  </code></pre>
  
  <p>I get this </p>
  
  <pre><code> /usr/local/lib/python3.6/dist-packages/lucid/misc/io/reading.py in &lt;module&gt;()
   31 from urllib.parse import urlparse, urljoin
   32 from future.moves.urllib import request
   33 from tensorflow import gfile
   34 from tempfile import gettempdir
   35 from io import BytesIO, StringIO
  
   ImportError: cannot import name 'gfile'
  </code></pre>
  
  <p>when I try:</p>
  
  <pre><code> import lucid.optvis.param as param
  </code></pre>
  
  <p>I get this error:</p>
  
  <pre><code>/usr/local/lib/python3.6/dist-packages/lucid/optvis/param/cppn.py in &lt;module&gt;()
   19 import numpy as np
   20 import tensorflow as tf
   21 from tensorflow.contrib import slim
   22 
   23 
  
   ModuleNotFoundError: No module named 'tensorflow.contrib'
  </code></pre>