old_contents: from nphelper import (
      block,
      cartesian_product,
      multi_dot,
      _multi_dot_matrix_chain_order,
  )
  
new_contents: from .nphelper import (
      block,
      cartesian_product,
      multi_dot,
      _multi_dot_matrix_chain_order,
  )
  
subject: Use explicit relative imports