title: What does "i" represent in Python .pyi extension?
body: <p>In Python, what does &quot;i&quot; represent in <code>.pyi</code> extension?</p>
  <p>In <a href="https://www.python.org/dev/peps/pep-0484/" rel="noreferrer" title="PEP-484">PEP-484</a>, it mentions <code>.pyi</code> is &quot;a stub file&quot; but no mnemonic help on the extension. So does the &quot;i&quot; mean &quot;Include&quot;? &quot;Implementation&quot;? &quot;Interface&quot;?</p>