title: How to handle unknown Vendors for mac-vendor-lookup
body: <p>I would like to create a dict based on MAC addresses and vendor, using the <code>mac-vendor-lookup</code> library. My code:</p>
  <pre><code>dicts = {}
  for index, value in mac_series.items():
      try:
          vendor = mac.lookup(value)
      except KeyError as e:
          print(f&quot;Error: {e}&quot;)
          vendor = &quot;UNKNOWN&quot;
      dicts[value] = vendor
  </code></pre>
  <p>This works fine, because I handle KeyErrors in the try/except. However I'd like to know why I get a KeyError in the first place, when the Mac addresses all follow a certain format. So I get mostly vendors coming back, but sometimes the occasional &quot;UNKNOWN&quot;. Is this an issue with an outdated lookup (despite using the latest pip package)?</p>