code: def readmask(filename, fieldname=None):
      
      f = scipy.io.loadmat(filename)
      if fieldname is not None:
          return f[fieldname].astype(np.uint8)
      else:
          validkeys = [
              k for k in list(f.keys()) if not (k.startswith('_') and k.endswith('_'))]
          if len(validkeys) < 1:
              raise ValueError('mask file contains no masks!')
          if len(validkeys) > 1:
              raise ValueError('mask file contains multiple masks!')
          return f[validkeys[0]].astype(np.uint8)
docs: Try to load a maskfile from a matlab(R) matrix file
  
      Inputs
      ------
      filename: string
          the input file name
      fieldname: string, optional
          field in the mat file. None to autodetect.
  
      Outputs
      -------
      the mask in a numpy array of type np.uint8