code: def is_tagged(self, layer):
          
          # we have a number of special names that are not layers but instead
          # attributes of "words" layer
          if layer == ANALYSIS:
              if WORDS in self and len(self[WORDS]) > 0:
                  return ANALYSIS in self[WORDS][0]
          elif layer == LAYER_CONLL:
              if LAYER_CONLL in self and len(self[LAYER_CONLL]) > 0:
                  return PARSER_OUT in self[LAYER_CONLL][0]
          elif layer == LAYER_VISLCG3:
              if LAYER_VISLCG3 in self and len(self[LAYER_VISLCG3]) > 0:
                  return PARSER_OUT in self[LAYER_VISLCG3][0]
          elif layer == LABEL:
              if WORDS in self and len(self[WORDS]) > 0:
                  return LABEL in self[WORDS][0]
          elif layer == CLAUSE_ANNOTATION:
              if WORDS in self and len(self[WORDS]) > 0:
                  return CLAUSE_ANNOTATION in self[WORDS][0]
          elif layer == WORDNET:
              if WORDS in self and len(self[WORDS]) > 0:
                  if ANALYSIS in self[WORDS][0] and len(self[WORDS][0][ANALYSIS]) > 0:
                      return WORDNET in self[WORDS][0][ANALYSIS][0]
          else:
              return layer in self
          return False
docs: Is the given element tokenized/tagged?