@@ -0,0 +1,63 @@
+import inspect
+ 
+# x is positional-only (default 0), e is positional-or-keyword (default 1)
+custom_power = lambda x=0, /, e=1: x**e
+ 
+ 
+def custom_equation(
+    x: int = 0, y: int = 0, /, a: int = 1, b: int = 1, *, c: int = 1
+) -> float:
+    """
+    Calculate (x**a + y**b) / c.
+ 
+    :param x: Positional-only base of the first term.
+    :type x: int
+    :param y: Positional-only base of the second term.
+    :type y: int
+    :param a: Exponent applied to x.
+    :type a: int
+    :param b: Exponent applied to y.
+    :type b: int
+    :param c: Keyword-only divisor.
+    :type c: int
+    :return: The value of (x**a + y**b) / c.
+    :rtype: float
+    """
+    return (x**a + y**b) / c
+ 
+ 
+_total_calls: int = 0
+_calls_by_caller: dict[str, int] = {}
+ 
+ 
+def fn_w_counter() -> tuple[int, dict[str, int]]:
+    """
+    Count how many times this function has been called, and by whom.
+ 
+    :return: A tuple of the total number of calls and a dictionary mapping
+        each caller's ``__name__`` to the number of calls it made.
+    :rtype: tuple[int, dict[str, int]]
+    """
+    global _total_calls
+    caller = inspect.currentframe().f_back.f_globals["__name__"]
+    _total_calls += 1
+    _calls_by_caller[caller] = _calls_by_caller.get(caller, 0) + 1
+    return _total_calls, dict(_calls_by_caller)
+ 
+ 
+if __name__ == "__main__":
+    assert custom_power(2) == 2
+    assert custom_power(2, 3) == 8
+    assert custom_power(2, e=2) == 4
+ 
+    assert custom_equation(2, 3) == 5.0
+    assert custom_equation(2, 3, 2) == 7.0
+    assert custom_equation(2, 3, 2, 3) == 31.0
+    assert custom_equation(3, 5, a=2, b=3, c=4) == 33.5
+    assert custom_equation(3, 5, 2, b=3, c=4) == 33.5
+    assert custom_equation(3, 5, 2, 3, c=4) == 33.5
+ 
+    for i in range(10):
+        fn_w_counter()
+    assert fn_w_counter() == (11, {"__main__": 11})
+    print("All examples pass.")