Added documentation to the reduce operator. Also added reduce calls t…

…o the chained observable class.

aioreactive/__init__.py

@@ -341,6 +341,18 @@ def merge(self, other: AsyncObservable[_TSource]) -> AsyncRx[_TSource]:
             AsyncRx.create,
         )
 
+    def reduce(
+        self, accumulator: Callable[[_TResult, _TSource], _TResult], initial: _TResult
+    ) -> "AsyncRx[_TResult]":
+        return pipe(self, reduce(accumulator, initial), AsyncRx[_TResult])
+
+    def reduce_async(
+        self,
+        accumulator: Callable[[_TResult, _TSource], Awaitable[_TResult]],
+        initial: _TResult,
+    ) -> "AsyncRx[_TResult]":
+        return pipe(self, reduce_async(accumulator, initial), AsyncRx[_TResult])
+
     def skip(self, count: int) -> AsyncObservable[_TSource]:
         """Skip items from start of the stream.
 
@@ -867,6 +879,17 @@ def reduce(
     accumulator: Callable[[_TResult, _TSource], _TResult],
     initial: _TResult,
 ) -> Callable[[AsyncObservable[_TSource]], AsyncObservable[_TResult]]:
+    """The reduce operator.
+
+    If an error occurs either in the accumulator or the source the subscription is disposed and the error is thrown.
+
+    Args:
+        accumulator: An accumulator function
+        initial: The initial value
+
+    Returns:
+        The reduce operator function
+    """
     from .transform import reduce as _reduce
 
     return _reduce(accumulator, initial)
@@ -876,6 +899,17 @@ def reduce_async(
     accumulator: Callable[[_TResult, _TSource], Awaitable[_TResult]],
     initial: _TResult,
 ) -> Callable[[AsyncObservable[_TSource]], AsyncObservable[_TResult]]:
+    """The async reduce operator.
+
+    See the `reduce` operator.
+
+    Args:
+        accumulator (Callable[[_TResult, _TSource], Awaitable[_TResult]]): An async accumulator function
+        initial (_TResult): The initial value
+
+    Returns:
+        Callable[[AsyncObservable[_TSource]], AsyncObservable[_TResult]]: The operator function
+    """
     from .transform import reduce_async as _reduce
 
     return _reduce(accumulator, initial)