code: def test_equal():
      b = Symbol("b")
      a = Symbol("a")
      e1 = a + b
      e2 = 2 * a * b
      e3 = a**3 * b**2
      e4 = a * b + b * a
      assert not e1 == e2
      assert not e1 == e2
      assert e1 != e2
      assert e2 == e4
      assert e2 != e3
      assert not e2 == e3
  
      x = Symbol("x")
      e1 = exp(x + 1 / x)
      y = Symbol("x")
      e2 = exp(y + 1 / y)
      assert e1 == e2
      assert not e1 != e2
      y = Symbol("y")
      e2 = exp(y + 1 / y)
      assert not e1 == e2
      assert e1 != e2
  
      e5 = Rational(3) + 2 * x - x - x
      assert e5 == 3
      assert 3 == e5
      assert e5 != 4
      assert 4 != e5
      assert e5 != 3 + x
      assert 3 + x != e5
  
file_path: sympy/sympy/core/tests/test_equal.py
imports: from sympy.core.numbers import Rational
  from sympy.core.symbol import Dummy, Symbol
  from sympy.functions.elementary.exponential import exp
label_desc: Use image node_id 1 for calling a global function with example usage: test_equal() without return types