class Graph:
    def __init__(self):
        # Using a dictionary where keys are nodes and values are lists of adjacent nodes
        self.graph = {}

    def add_node(self, node):
        if node not in self.graph:
            self.graph[node] = []

    def add_edge(self, u, v, bidirectional=False):
        # Ensure both nodes exist
        self.add_node(u)
        self.add_node(v)
        # Add edge from u to v
        self.graph[u].append(v)
        # If bidirectional, add edge from v to u as well
        if bidirectional:
            self.graph[v].append(u)

    def get_neighbors(self, node):
        return self.graph.get(node, [])

    def print_graph(self):
        for node, neighbors in self.graph.items():
            print(f"{node}: {neighbors}")

# Example Usage:
my_graph = Graph()
my_graph.add_edge("A", "B", bidirectional=True)
my_graph.add_edge("A", "C")
my_graph.add_edge("B", "D")
my_graph.add_node("E") # Add a disconnected node

print("Graph Adjacency List:")
my_graph.print_graph()

print(f"
Neighbors of A: {my_graph.get_neighbors('A')}")
print(f"Neighbors of B: {my_graph.get_neighbors('B')}")
print(f"Neighbors of E: {my_graph.get_neighbors('E')}")