code: public synchronized boolean contains(EvidenceType type, Confidence confidence) {
          if (null == type) {
              return false;
          }
          final Set<Evidence> col;
          switch (type) {
              case VENDOR:
                  col = vendors;
                  break;
              case PRODUCT:
                  col = products;
                  break;
              case VERSION:
                  col = versions;
                  break;
              default:
                  return false;
          }
          for (Evidence e : col) {
              if (e.getConfidence().equals(confidence)) {
                  return true;
              }
          }
          return false;
      }
docs: Returns whether or not the collection contains evidence of a specified
  type and confidence.
  
  @param type the type of evidence (vendor, product, version)
  @param confidence A Confidence value.
  @return boolean.