Simple Writer monad demo in Python3

monad.py

class Writer:
    
    def __init__(self, value, log: str = ""):
        self._value = value
        self._log = log
    
    # For decorating individual functions with messages
    @staticmethod
    def explain(message: str):
        def decorator(modification: callable):
            def modification_with_log(*args, **kwargs):
                return Writer(value=modification(*args, **kwargs),
                              log=message)
            return modification_with_log
        return decorator
        
    @property
    def result(self):
        return self._value
    
    @staticmethod
    def unit(value):
        return Writer(value)
    
    # sig: (A => M[B]) => M[B]
    def flatMap(self, f):
        newWriter = f(self._value)
        return Writer(newWriter._value, self._log+"\n"+newWriter._log)
    
    # sig: (A => B) => M[B]
    def map(self, f):
        return self.flatMap(lambda value: self.unit(f(value)))
        
    def __repr__(self):
        return f"{self._log}"
    
    # So we can use '>>' as a pipe operator
    def __rshift__(self, writerGenerator: callable):
        return self.flatMap(writerGenerator)

writer.py

import monad
        
def writer_test():
    
    def modify(f, msg):
        return lambda x: monad.Writer(value=f(x), log=msg)

    pipeline = monad.Writer(2) >> \
                modify(lambda x: x+3, "1) Added 3") >> \
                modify(lambda x: 4*x, "2) Multiplied by 4") >> \
                modify(lambda x: x**2, "3) Raised to the 2nd power")

    
    print(f"The result of the pipeline is {pipeline.result}\n")
    print("The pipeline log is :")
    print(pipeline)
        
    # Pipeline from decorated functions

    @monad.Writer.explain("1) Added 3")
    def step1(x):
        return x+3
        
    @monad.Writer.explain("2) Multiplied by 4")
    def step2(x):
        return 4*x
        
    @monad.Writer.explain("3) Raised to the 2nd power")
    def step3(x):
        return x**2
    
    second_pipeline = monad.Writer(2) >> \
                        step1 >> \
                        step2 >> \
                        step3
                        
    print(f"\nDecorator-constructed pipeline yields the same result - {second_pipeline.result}")

    print(second_pipeline)


if __name__ == "__main__":
    writer_test()