code: def butter_bandpass_filter(self, data, lowcut, highcut, fs, order=5):
      b, a = self.butter_bandpass(lowcut, highcut, fs, order=order)
      y = signal.lfilter(b, a, data)
      return y
  
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 6 for calling the Process obj's underlying member method code with example usage: obj.butter_bandpass_filter(data, lowcut, highcut, fs, order) and returns: y