code: public void assertOneOrMore(final String propertyName,
              final PropertyList properties) throws ValidationException {
  
          if (properties.getProperties(propertyName).size() < 1) {
              throw new ValidationException(ASSERT_ONE_OR_MORE_MESSAGE, new Object[] {propertyName});
          }
      }
docs: Ensure a property occurs at least once.
  
  @param propertyName
  the property name
  @param properties
  a list of properties to query
  @throws ValidationException
  when the specified property occurs more than once