code: def test_issue_18653():
      x, y, z = symbols("x y z")
      f, g, h = symbols("f g h", cls=Function, args=(x, y))
      f, g, h = f(), g(), h()
      expr2 = f.diff(x) * h.diff(z)
      assert euler(expr2, (f,), (x, y)) == []
  
file_path: sympy/sympy/calculus/tests/test_euler.py
imports: from sympy.core.function import Derivative, Function
  from sympy.core.relational import Eq
  from sympy.core.symbol import Symbol, symbols
  from sympy.functions.elementary.trigonometric import cos, sin
  from sympy.testing.pytest import raises
  from sympy.calculus.euler import euler_equations
label_desc: Use image node_id 6 for calling a global function with example usage: test_issue_18653() without return types