code: def cp_key(c, ring):
      """
      Key for comparing critical pairs.
      """
      return (
          lbp_key(lbp(c[0], ring.zero, Num(c[2]))),
          lbp_key(lbp(c[3], ring.zero, Num(c[5]))),
      )
  
imports: from sympy.core.symbol import Dummy
  from sympy.polys.monomials import monomial_mul, monomial_lcm, monomial_divides, term_div
  from sympy.polys.orderings import lex
  from sympy.polys.polyerrors import DomainError
  from sympy.polys.polyconfig import query
label_desc: Use image node_id 18 for calling a global function with example usage: cp_key(c, ring) and returns: lbp_key,  lbp_key