docs: def sniff_link(url):
      """performs basic heuristics to detect what the URL is"""
  
      protocol = None
      link = url.strip()
  
      # heuristics begin
      if inurl(['service=CSW', 'request=GetRecords'], link):
          protocol = 'OGC:CSW'
      elif inurl(['service=SOS', 'request=GetObservation'], link):
          protocol = 'OGC:SOS'
      elif inurl(['service=WCS', 'request=GetCoverage'], link):
          protocol = 'OGC:WCS'
      elif inurl(['service=WFS', 'request=GetFeature'], link):
          protocol = 'OGC:WFS'
      elif inurl(['service=WMS', 'request=GetMap'], link):
          protocol = 'OGC:WMS'
      elif inurl(['service=WPS', 'request=Execute'], link):
          protocol = 'OGC:WPS'
      elif inurl(['arcims'], link):
          protocol = 'ESRI:ArcIMS'
      elif inurl(['arcgis'], link):
          protocol = 'ESRI:ArcGIS'
      elif inurl(['mpk'], link, 'end'):
          protocol = 'ESRI:MPK'
      elif inurl(['opendap'], link):
          protocol = 'OPeNDAP:OPeNDAP'
      elif inurl(['ncss'], link):
          protocol = 'UNIDATA:NCSS'
      elif inurl(['cdmremote'], link):
          protocol = 'UNIDATA:CDM'
      elif inurl(['gml'], link, 'end'):
          protocol = 'OGC:GML'
      elif inurl(['htm', 'html', 'shtml'], link, 'end'):
          protocol = 'WWW:LINK'
      # extra tests
      elif all([inurl(['census.gov/geo/tiger'], link),
                inurl(['zip'], link, 'end')]):
          protocol = 'ESRI:SHAPEFILE'
      elif inurl(['7z', 'bz2', 'gz', 'rar', 'tar.gz', 'tgz', 'zip'],
                 link, 'end'):
          protocol = 'WWW:DOWNLOAD'
      elif inurl(['kml', 'kmz'], link, 'end'):
          protocol = 'OGC:KML'
      else:
          LOGGER.info('No link type detected')
  
      return protocol