class Node:
    def __init__(self):
        self.is_infected = False


class Edge:
    def __init__(self, node_a: Node, node_b: Node, weight: float):
        self.node_a = node_a
        self.node_b = node_b
        self.weight = weight


class Graph:
    def __init__(self):
        self.edges = []

    def add_edge(self, edge: Edge):
        self.edges.append(edge)