code: public boolean containsContextsWithACModel(AbstractACModel acModel) {
          for (ProcessContext context : getComponents()) {
              if (context.getACModel().equals(acModel)) {
                  return true;
              }
          }
          return false;
      }
docs: Checks if there are contexts whose access control model equals the given
  model.
  
  @param acModel The access control model.
  @return <code>true</code> if there is at least one such context;<br>
  <code>fasle</code> otherwise.