def METHOD_NAME(self, cost_matrix: np.ndarray, bbox_pairs: List) -> np.ndarray:
    """
    Based on IoU for each pair of bbox, assign the associated value in cost matrix
    Args:
        cost_matrix: np.ndarray, initialized 2D array with target dimensions
        bbox_pairs: list of bbox pair, in each pair, iou value is stored
    Return:
        np.ndarray, cost_matrix with assigned values
    """
    for pair in bbox_pairs:
        # assign -1 for IoU above threshold pairs, algorithms will minimize cost
        cost_matrix[pair["idx"]][pair["prev_idx"]] = -1
    return cost_matrix