title: Can't find the modules that have been installed by pip
body: <p>I use PyCharm, normally I install 3rd party libraries with the <strong>Project Interpreter</strong> in PyCharm. Today I installed <strong>plotly</strong> by running <code>pip install plotly==2.7</code> in the terminal. But when I tried to import it, I got an unresolved reference 'plotly' warning in the editor. How can I solve it?<br>
  I got this error when I run the code <code>ModuleNotFoundError: No module named 'plotly'</code></p>