Scheduler first commit

examples/schedule/schedule_lib/null_node.py

@@ -0,0 +1,25 @@
+import functools
+from symtable import Function
+from typing import List, Callable, Generator
+
+from api.od import ODAPI
+from .singleton import Singleton
+
+from .exec_node import ExecNode
+
+class NullNode(ExecNode, metaclass=Singleton):
+    def __init__(self):
+        ExecNode.__init__(self, out_connections=0)
+
+    def execute(self, od: ODAPI) -> Generator | None:
+        raise Exception('Null node should already have terminated the schedule')
+
+    @staticmethod
+    def terminate(od: ODAPI):
+        return None
+        yield # verrrry important line, dont remove this unreachable code
+
+    def generate_dot(self, nodes: List[str], edges: List[str], visited: set[int]) -> None:
+        if self.id in visited:
+            return
+        nodes.append(f"{self.id}[label=Null]")