code: def test_qexpr_subs():
      q1 = QExpr(x, y)
      assert q1.subs(x, y) == QExpr(y, y)
      assert q1.subs({x: 1, y: 2}) == QExpr(1, 2)
  
file_path: sympy/sympy/physics/quantum/tests/test_qexpr.py
imports: from sympy.core.numbers import Integer
  from sympy.core.symbol import Symbol
  from sympy.physics.quantum.qexpr import QExpr, _qsympify_sequence
  from sympy.physics.quantum.hilbert import HilbertSpace
  from sympy.core.containers import Tuple
label_desc: Use image node_id 4 for calling a global function with example usage: test_qexpr_subs() without return types