code: def test_parse_expr():
      a, b = symbols("a, b")
      # tests issue_16393
      assert parse_expr("a + b", {}) == a + b
      raises(SympifyError, lambda: parse_expr("a + ", {}))
  
      # tests Transform.visit_Constant
      assert parse_expr("1 + 2", {}) == S(3)
      assert parse_expr("1 + 2.0", {}) == S(3.0)
  
      # tests Transform.visit_Name
      assert parse_expr("Rational(1, 2)", {}) == S(1) / 2
      assert parse_expr("a", {"a": a}) == a
  
      # tests issue_23092
      with warnings.catch_warnings():
          warnings.simplefilter("error")
          assert parse_expr("6 * 7", {}) == S(42)
  
imports: from sympy.core.singleton import S
  from sympy.core.symbol import symbols
  from sympy.parsing.ast_parser import parse_expr
  from sympy.testing.pytest import raises
  from sympy.core.sympify import SympifyError
  import warnings
label_desc: Use image node_id 1 for calling a global function with example usage: test_parse_expr() without return types