title: Cannot import name '_png' from 'matplotlib'
body: <p>I want to use matplotlib instead kivy_garden.graph. Actually, I tried <a href="https://stackoverflow.com/a/44922317/8780918">this code</a> to check if it works for me. I've had some problems with installing matplotlib but I have successfully(or not) done that.</p>
  <p>When I started the code I got <code>from matplotlib import _png ImportError: cannot import name '_png' from 'matplotlib' (D:\PyCharmProjects\kivyApp\venv\lib\site-packages\matplotlib\__init__.py)</code>
  I reinstalled matplotlib and pip, tried another version of matplotlib and I don't know why it is not working for me.
  I have <strong>Python 3.7.5</strong>, <strong>pip 20.2.4</strong> and <strong>matplotlib 3.3.3</strong></p>