code: def complete_features(db):
      
      for feature in db.all_features():
          gene_id = feature.attributes.get('gene_id', [None])[0]
          transcript_id = feature.attributes.get('transcript_id', [None])[0]
          if gene_id and transcript_id and feature.featuretype != "transcript":
              yield feature
docs: iterator returning features which are complete (have a 'gene_id' and a
      'transcript_id')