code: def cal_angle(self, v1):
      theta = np.arccos(min(1, v1[0] / (np.linalg.norm(v1) + 10e-8)))
      return 2 * math.pi - theta if v1[1] < 0 else theta
  
file_path: EasyOCR/trainer/craft/data/pseudo_label/make_charbox.py
imports: import os
  import random
  import math
  import numpy
  import cv2
  import torch
  from data import imgproc
  from data.pseudo_label.watershed import exec_watershed_by_version
label_desc: Use image node_id 8 for calling the PseudoCharBoxBuilder obj's underlying member method code with example usage: obj.cal_angle(v1) and returns: unknown