code: def _is_zero_after_expand_mul(x):
      """Tests by expand_mul only, suitable for polynomials and rational
      functions."""
      return expand_mul(x) == 0
  
file_path: sympy/sympy/matrices/utilities.py
imports: from contextlib import contextmanager
  from threading import local
  from sympy.core.function import expand_mul
label_desc: Use image node_id 6 for calling a global function with example usage: _is_zero_after_expand_mul(x) and returns: unknown