class GraphDB:
    def __init__(self):
        self.nodes = {}  # node_id -> properties
        self.edges = {}  # node_id -> set of connected node_ids

    def add_node(self, node_id, **properties):
        self.nodes[node_id] = properties
        self.edges.setdefault(node_id, set())

    def add_edge(self, from_node, to_node):
        if from_node in self.nodes and to_node in self.nodes:
            self.edges[from_node].add(to_node)
            self.edges[to_node].add(from_node)  # undirected graph

    def get_node(self, node_id):
        return self.nodes.get(node_id)

    def get_neighbors(self, node_id):
        return self.edges.get(node_id, set())

    def find_nodes_by_property(self, key, value):
        return [nid for nid, props in self.nodes.items() if props.get(key) == value]

    def shortest_path(self, start, end):
        from collections import deque
        visited = set()
        queue = deque([(start, [start])])

        while queue:
            current, path = queue.popleft()
            if current == end:
                return path
            visited.add(current)
            for neighbor in self.edges.get(current, []):
                if neighbor not in visited:
                    queue.append((neighbor, path + [neighbor]))
        return None
    
 
g = GraphDB()
g.add_node("A", type="Person", name="Alice")
g.add_node("B", type="Person", name="Bob")
g.add_node("C", type="City", name="Phoenix")
g.add_edge("A", "B")
g.add_edge("A", "C")
g.add_edge("B", "C")

print(g.get_neighbors("A"))  # {'B', 'C'}
print(g.find_nodes_by_property("type", "Person"))  # ['A', 'B']
print(g.shortest_path("B", "C"))  # ['B', 'A', 'C']