title: Difference between mypy vs mypy-lang vs pyls-mypy python packages
body: <p>I am exploring static type checker for Python and came across different packages while setting up Visual Studio Code. I have installed <code>python-language-server</code> for linting and formatting. I came across <code>mypy.exe</code> and <code>mypyls.exe</code> executables.</p>
  
  <p>I could do,</p>
  
  <p><code>pip install mypy</code></p>
  
  <p><code>pip install mypy-lang</code></p>
  
  <p><code>pip install pyls-mypy</code></p>
  
  <p>All the above three works. But,</p>
  
  <ol>
  <li>I would like to know the difference between <code>mypy</code>, <code>mypy-lang</code> and <code>pyls-mypy</code> packages?</li>
  <li>Which of these is used for enabling the Type-Checker (or all the 3 are needed)?</li>
  <li>Are these packages in any way related to the <code>python-language-server</code> ? If yes, how ?</li>
  </ol>