__init__.py

class Strategy:
    registered = []

    def __init__(self, func):
        self._func = func
        Strategy.registered.append(func)

    def __call__(self, *args, **kwargs):
        return self._func(*args, **kwargs)

functions.py

from strategy import Strategy


@Strategy
def strategy_1(x, y):
    return x + y


@Strategy
def strategy_2(x, y):
    return x - y


print(Strategy.registered)

strategy.md

Sample of strategy with registration in import time