code: def butter_bandpass(self, lowcut, highcut, fs, order=5):
      nyq = 0.5 * fs
      low = lowcut / nyq
      high = highcut / nyq
      b, a = signal.butter(order, [low, high], btype="band")
      return b, a
  
file_path: heart-rate-measurement-camera/process.py
imports: import cv2
  import numpy
  import time
  from face_detection import FaceDetection
  from scipy import signal
  from face_utilities import Face_utilities
  from signal_processing import Signal_processing
  from imutils import face_utils
label_desc: Use image node_id 5 for calling the Process obj's underlying member method code with example usage: obj.butter_bandpass(lowcut, highcut, fs, order) and returns: b,  a