old_contents: """ Unification in SymPy
  
  See sympy.unify.core docstring for algorithmic details
  
  See http://matthewrocklin.com/blog/work/2012/11/01/Unification/ for discussion
  """
  
  import core
  import usympy
  import rewrite
  from usympy import unify, patternify, rebuild
  from rewrite import rewriterule
  
new_contents: """ Unification in SymPy
  
  See sympy.unify.core docstring for algorithmic details
  
  See http://matthewrocklin.com/blog/work/2012/11/01/Unification/ for discussion
  """
  
  from usympy import unify, patternify, rebuild
  from rewrite import rewriterule
  
subject: remove submodule imports