Validation Descriptor

Write a descriptor class IntegerRange that restricts a class attribute to integers between a minimum and maximum value (inclusive). The __init__(self, min_val, max_val) constructor should accept min_val and max_val. If __set__(self, instance, value) is called with a value that is not an integer, or is outside the specified range, raise a ValueError.

Also write a class Planet that uses the descriptor for its gravity attribute:

class Planet:
    gravity = IntegerRange(1, 100)
    def __init__(self, name, gravity):
        self.name = name
        self.gravity = gravity

Finally, write a helper function test_descriptor(name, gravity) that instantiates Planet(name, gravity). If it succeeds, return the string '{name} is at {gravity}g'. If a ValueError is raised, catch it and return 'invalid gravity'.