code: def _find_matcher(self, alias):
          
          matcher = lookup(alias)
          if not matcher:
              msg = 'Matcher "%s" not found' % alias
  
              # Try to find similarly named matchers to help the user
              similar = suggest(alias, max=3, cutoff=0.5)
              if len(similar) > 1:
                  last = similar.pop()
                  msg += '. Perhaps you meant to use %s or %s?' % (', '.join(similar), last)
              elif len(similar) > 0:
                  msg += '. Perhaps you meant to use %s?' % similar.pop()
  
              raise KeyError(msg)
  
          return matcher
docs: Finds a matcher based on the given alias or raises an error if no
              matcher could be found.