docs: def max_diff(dset1,dset2):
      '''calculates maximal voxel-wise difference in datasets (in %)
  
      Useful for checking if datasets have the same data. For example, if the maximum difference is
      < 1.0%, they're probably the same dataset'''
      for dset in [dset1,dset2]:
          if not os.path.exists(dset):
              nl.notify('Error: Could not find file: %s' % dset,level=nl.level.error)
              return float('inf')
      try:
          dset1_d = nib.load(dset1)
          dset2_d = nib.load(dset2)
          dset1_data = dset1_d.get_data()
          dset2_data = dset2_d.get_data()
      except IOError:
          nl.notify('Error: Could not read files %s and %s' % (dset1,dset2),level=nl.level.error)
          return float('inf')
      try:
          old_err = np.seterr(divide='ignore',invalid='ignore')
          max_val = 100*np.max(np.ma.masked_invalid(np.double(dset1_data - dset2_data) / ((dset1_data+dset2_data)/2)))
          np.seterr(**old_err)
          return max_val
      except ValueError:
          return float('inf')