code: def test_sig_key():
      s1 = sig((0,) * 3, 2)
      s2 = sig((1,) * 3, 4)
      s3 = sig((2,) * 3, 2)
  
      assert sig_key(s1, lex) > sig_key(s2, lex)
      assert sig_key(s2, lex) < sig_key(s3, lex)
  
imports: from sympy.polys.groebnertools import groebner, sig, sig_key, lbp, lbp_key, critical_pair, cp_key, is_rewritable_or_comparable, Sign, Polyn, Num, s_poly, f5_reduce, groebner_lcm, groebner_gcd, is_groebner, is_reduced
  from sympy.polys.fglmtools import _representing_matrices
  from sympy.polys.orderings import lex, grlex
  from sympy.polys.rings import ring, xring
  from sympy.polys.domains import ZZ, QQ
  from sympy.testing.pytest import slow
  from sympy.polys import polyconfig
label_desc: Use image node_id 20 for calling a global function with example usage: test_sig_key() without return types