old_contents: 
  import argparse
  import numpy as np
  import os
  import scipy.io.wavfile as wavfile
  import scipy.optimize.nnls as nnls
  import yaml
  
  import medleydb as mdb
  
  
  def flatten(w):
      return w.T.ravel()
  
  
  def loadmono(filename):
      _, w = wavfile.read(filename)
      w = np.square(w.sum(axis=1))
      return w
  
  
  def analyze_mix(mtrack):
  
      mixfile = mtrack.mix_path
      mix_audio = loadmono(mixfile)
  
      stems = mtrack.stems
      stem_indices = list(stems.keys())
      stem_files = [stems[k].file_path for k in stem_indices]
      stem_audio = np.vstack(
          [loadmono(_) for _ in stem_files]
      )
  
      coefs, _ = nnls(stem_audio.T, mix_audio.T)
  
      mixing_coeffs = {
          int(i): float(c) for i, c in zip(stem_indices, coefs)
      }
      return mixing_coeffs
  
  
  def main(args):
      mtracks = mdb.load_all_multitracks()
      mix_coefs = dict()
      for mtrack in mtracks:
          mix_coefs[os.path.basename(mtrack.mix_path)] = analyze_mix(mtrack)
      with open(args.output_path, 'w') as fdesc:
          yaml.dump(mix_coefs, fdesc)
  
  
  if __name__ == "__main__":
      parser = argparse.ArgumentParser(
          description="Creat ground truth seed files from medleydb")
      parser.add_argument("output_path",
                          type=str,
                          help="Path to save mixing coefficients file.")
      main(parser.parse_args())
  
new_contents: 
  import argparse
  import numpy as np
  import scipy.io.wavfile as wavfile
  import scipy.optimize.nnls as nnls
  import yaml
  
  import medleydb as mdb
  
  
  def flatten(w):
      return w.T.ravel()
  
  
  def loadmono(filename):
      _, w = wavfile.read(filename)
      w = np.abs(w.sum(axis=1))
      return w
  
  
  def analyze_mix(mtrack):
  
      mixfile = mtrack.mix_path
      mix_audio = loadmono(mixfile)
  
      stems = mtrack.stems
      stem_indices = list(stems.keys())
      stem_files = [stems[k].file_path for k in stem_indices]
      stem_audio = np.vstack(
          [loadmono(_) for _ in stem_files]
      )
  
      coefs, _ = nnls(stem_audio.T, mix_audio.T)
  
      mixing_coeffs = {
          int(i): float(c) for i, c in zip(stem_indices, coefs)
      }
      return mixing_coeffs
  
  
  def main(args):
      mtracks = mdb.load_all_multitracks()
      mix_coefs = dict()
      for mtrack in mtracks:
          mix_coefs[mtrack.track_id] = analyze_mix(mtrack)
      with open(args.output_path, 'w') as fdesc:
          yaml.dump(mix_coefs, fdesc)
  
  
  if __name__ == "__main__":
      parser = argparse.ArgumentParser(
          description="Creat ground truth seed files from medleydb")
      parser.add_argument("output_path",
                          type=str,
                          help="Path to save mixing coefficients file.")
      main(parser.parse_args())
  
subject: use abs instead of square