Added improved models

src/cpl_reactive_extensions/abc/observer.py

@@ -0,0 +1,20 @@
+from abc import abstractmethod, ABC
+
+from cpl_core.type import T
+
+
+class Observer(ABC):
+    def __init__(self):
+        ABC.__init__(self)
+
+    @abstractmethod
+    def next(self, value: T):
+        pass
+
+    @abstractmethod
+    def error(self, ex: Exception):
+        pass
+
+    @abstractmethod
+    def complete(self):
+        pass