def METHOD_NAME(self, comp_type):
    """Returns reference data."""
    if comp_type == "single_input":
        def a_plus_1_ref(a):
            return a + 1
        return a_plus_1_ref
    else:
        def a_plus_b_plus_1_ref(a, b):
            return a + b + 1
        return a_plus_b_plus_1_ref