feat: allow `node.id` to be specified and not automatically generated (#422)

* allow node.id to be specified and not generated

* typing suport for context functions

Co-authored-by: Ivan Melnychuk <ivan.melnychuk@pg3.ch>

diagrams/__init__.py

@@ -15,25 +15,25 @@ __diagram = contextvars.ContextVar("diagrams")
 __cluster = contextvars.ContextVar("cluster")
 
 
-def getdiagram():
+def getdiagram() -> "Diagram":
     try:
         return __diagram.get()
     except LookupError:
         return None
 
 
-def setdiagram(diagram):
+def setdiagram(diagram: "Diagram"):
     __diagram.set(diagram)
 
 
-def getcluster():
+def getcluster() -> "Cluster":
     try:
         return __cluster.get()
     except LookupError:
         return None
 
 
-def setcluster(cluster):
+def setcluster(cluster: "Cluster"):
     __cluster.set(cluster)
 
 
@@ -283,13 +283,13 @@ class Node:
 
     _height = 1.9
 
-    def __init__(self, label: str = "", **attrs: Dict):
+    def __init__(self, label: str = "", *, nodeid: str = None, **attrs: Dict):
         """Node represents a system component.
 
         :param label: Node label.
         """
-        # Generates an ID for identifying a node.
+        # Generates an ID for identifying a node, unless specified
-        self._id = self._rand_id()
+        self._id = nodeid or self._rand_id()
         self.label = label
 
         # fmt: off