code: def _sum_free_test(subset):
      """
      Checks if subset is sum-free(There are no x,y,z in the subset such that
      x + y = z)
      """
      for i in subset:
          for j in subset:
              assert (i + j in subset) is False
  
file_path: sympy/sympy/combinatorics/tests/test_schur_number.py
imports: from sympy.core import S, Rational
  from sympy.combinatorics.schur_number import schur_partition, SchurNumber
  from sympy.core.random import _randint
  from sympy.testing.pytest import raises
  from sympy.core.symbol import symbols
label_desc: Use image node_id 1 for calling a global function with example usage: _sum_free_test(subset) without return types