code: protected <T> T getProperty(String alias, Class<T> targetType) {
  		String k = resolveKey(alias);
  		return k == null ? null : resolver.getProperty(k, targetType);
  	}
docs: Returns the value of first property represented by the provided alias
  that has a value (not {@code null}).
  
  @param alias
  the property alias to resolve
  @param targetType
  the expected type of the property value
  @param <T>
  the type of the property value
  @return The property value or null