code: def singleChoiceParam(parameters, name, type_converter = str):
      
      param = parameters.find(".//SingleChoiceParam[@Name='{name}']".format(name=name))
      value = int(param.find('Value').text)
      values = param.find('Values')
      if value < 0:
          return value
      return type_converter(values[value].text)
docs: single choice parameter value. Returns -1 if no value was chosen.
      :param parameters: the parameters tree.
      :param name: the name of the parameter.
      :param type_converter: function to convert the chosen value to a different type (e.g. str, float, int). default = 'str