First working version

.gitignore

@@ -1,3 +1,3 @@
+# Created by venv; see https://docs.python.org/3/library/venv.html
+*
 venv
-__pycache__
-*.pyc

nodes/manager.py

@@ -1,5 +1,40 @@
-# Create here the NodeManager Class
+from .node import Node
+from typing import List
 
 
 class NodeManager:
-    pass
+    nodes: List[Node]
+
+    def __init__(self, nodes: List[Node]):
+        if not isinstance(nodes, list):
+            raise ValueError("Must pass a list of nodes.")
+
+        self.nodes = nodes.copy()
+
+
+    def __getitem__(self, index) -> Node:
+        return self.nodes[index]
+
+
+    def __len__(self) -> int:
+        return len(self.nodes)
+
+
+    def remove(self, node: Node) -> None:
+        index = self.nodes.index(node)
+        self.nodes.pop(index)
+
+
+    def remove_cascade(self, node: Node) -> None:
+        index = self.nodes.index(node)
+        stack = []
+        stack.append(self.nodes.pop(index))
+        while stack:
+            node = stack.pop()
+            to_remove = []
+            for item  in self.nodes:
+                if item.parent == node.id:
+                    stack.append(item)
+                    to_remove.append(item)
+            for item in to_remove:
+                self.nodes.remove(item)

nodes/node.py

@@ -2,4 +2,21 @@
 
 
 class Node:
-    pass
+    id: int
+    parent: int
+    def __init__(self, id: int, parent: int):
+        if not isinstance(id, int):
+            raise ValueError("id must be a integer.")
+
+        if not isinstance(parent, int):
+            raise ValueError("parent must be a integer.")
+
+        if parent >= id:
+            raise ValueError("A Node parent cannot be greater or equal to it's id.")
+
+        self.id = id
+        self.parent = parent
+
+
+    def __repr__(self):
+        return f"Node({self.id}, {self.parent})"