code: def _match_vcs_scheme(url):
      # type: (str) -> Optional[str]
      
      from pipenv.patched.notpip._internal.vcs import VcsSupport
      for scheme in VcsSupport.schemes:
          if url.lower().startswith(scheme) and url[len(scheme)] in '+:':
              return scheme
      return None
docs: Look for VCS schemes in the URL.
  
      Returns the matched VCS scheme, or None if there's no match.