Added subject

src/cpl_reactive_extensions/subject.py

@@ -3,15 +3,18 @@ from cpl_reactive_extensions.observable import Observable
 
 
 class Subject(Observable):
-    def __init__(self):
+    def __init__(self, _t: type):
         Observable.__init__(self)
 
+        self._t = _t
         self._value: T = None
 
     @property
     def value(self) -> T:
         return self._value
 
-    def emit(self, value: T):
+    def next(self, value: T):
+        if not isinstance(value, self._t):
+            raise TypeError(f"Expected {self._t.__name__} not {type(value).__name__}")
+
         self._value = value
-        self._subscriptions()