code: public static Collection<BioEntityMention> getProteins(
              Collection<BioEntityMention> mentions) {
          ArrayList<BioEntityMention> ret = new ArrayList<BioEntityMention>();
          for (BioEntityMention mention : mentions) {
              if (mention.getSpecificType() != null
                      && mention.getSpecificType().startsWith("G#protein"))
                  ret.add(mention);
          }
          return ret;
      }
docs: Filters mentions that are proteins