code: def lookup(cls, name):
          
          try:
              field = cls.FIELDS[name]
          except KeyError:
              # Is it a custom attribute?
              field = TorrentProxy.add_manifold_attribute(name)
  
          return {"matcher": field._matcher} if field else None
docs: Try to find field C{name}.
  
              @return: Field descriptions, see C{matching.ConditionParser} for details.