Either.bind function doesn't support type hint as well

[fResult]

Either.bind function doesn't support type hint as well

Problem

The average functoion receives list[float], and returns Either[ErrorMessage, float].

So the avg_result type should be Either[ErrorMessage, float], not Ether[ErrorMessage, list[list[str]]].

But when I use bind function, it will return only the type of Either source.

Reproduce:

https://github.com/fResult/Just-Python/blob/fc32a08509741a5dff6a45d922175890e5a86478/worksheets/csv_use_either.py#L94-L100

Current implementation of the bind function

I found that the bind method signature is receive Callable[[S], 'Either[M, T]' which M, and T generic types are from the Either its class.

But I think it should be like this instead...

My Solution

I'm a new Python user, and I'm not an advanced functional programmer.
So, I'm not sure that my solution will break something, or not.
.
.
Let the M, and T generic types refer to generic M, and T of bind method itself.

-    def bind(
+    def bind[M, T](
             self: 'Either[M, S]', kleisli_function: Callable[[S], 'Either[M, T]']
     ) -> 'Either[M, T]':
         """ See Monad.bind """
         if self.is_left(): # pylint: disable=no-else-return
             return self
         else:
             return kleisli_function(self.value)

We will get the result of Either.bind like this.