code: def lbp_key(f):
      """
      Key for comparing two labeled polynomials.
      """
      return (sig_key(Sign(f), Polyn(f).ring.order), -Num(f))
  
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 15 for calling a global function with example usage: lbp_key(f) and returns: sig_key,  unknown