@classmethod
def RegisterHelpers(cls, helper_classes):
    """Registers helper classes.

    The helper classes are identified based on their lower case name.

    Args:
      helper_classes (list[type]): class objects of the argument helpers.

    Raises:
      KeyError: if helper class is already set for the corresponding name.
    """
    for helper_class in helper_classes:
        cls.RegisterHelper(helper_class)
