code: def get_unchanged(src_list, npred_dict_new,
                    npred_dict_old,
                    npred_threshold=1e4,
                    frac_threshold=0.9):
      
      o = []
      for s in src_list:
          npred_new = npred_dict_new[s]
          if npred_new < npred_threshold:
              o += [s]
              continue
          if npred_dict_old is None:
              npred_old = 0.
          else:
              npred_old = npred_dict_old[s]
          frac = npred_old / npred_new
          if frac > frac_threshold:
              o += [s]
      return o
docs: Compare two dictionarys of npreds, and get the list of sources
      than have changed less that set thresholds
  
      Parameters
      ----------
  
      src_list : list
          List of sources to examine
  
      npred_dict_new : dict
          Dictionary mapping source name to npred for the current weights file
  
      npred_dict_old : dict
          Dictionary mapping source name to npred for the previous weights file
  
      npred_threshold : float
          Minimum value of npred above which to consider sources changed
  
      frac_threshold : float
          Value of npred_old / npred_new above which to consider sources unchanged
  
  
      Returns
      -------
  
      l : list
         Names of 'unchanged' sources