import random


def choose_true_edges(edges, K):
    """
    Randomly choose a fixed number of existing edges
    :param edges: The graph's edges
    :param K: Fixed number of edges to choose
    :return: A list of K true edges
    """
    indexes = random.sample(range(1, len(edges)), K)
    true_edges = []
    for i in indexes:
        true_edges.append(edges[i])
    return true_edges