title: Numpy array/asarray leak?
body: <p>Processing images on the server with pytorch and facing memory issues. In particular:</p>
  <p>Scenario 1:</p>
  <pre><code>#before execution memory used is 1518
  temp = PIL.Image.open(im) #no leak
  del im
  del temp
  gc.collect()
  #after execution x5 times memory used is 1518
  </code></pre>
  <p>Scenario 2:</p>
  <pre><code>#before execution memory used is 1518
  temp = PIL.Image.open(im) #no leak
  del im
  temp2 = np.array(temp) #leak? (asarray has same behaviour)
  del temp
  temp2 = None
  del temp2
  gc.collect()
  #after execution x5 times memory used is 2385
  </code></pre>
  <p>Details:</p>
  <pre><code>numpy==1.19.0
  python==3.6.9
  flask
  apache2
  libapache2-mod-wsgi-py3
  virtualenv
  watching memory using 'watch free -m'
  </code></pre>
  <p>I do not think this is flask or wsgi -related</p>
  <p>However, if I do a simple experiment in python3 environment:</p>
  <pre><code>#before execution memory used is 2418
  a = [random.random()]*100000000
  b = np.array(a)
  del a
  del b
  #after execution memory used is 2418
  </code></pre>