code: def test_symbol_repr():
      x, y = Symbol("x"), Symbol("y")
      expr = x * x + y * 2
      assert str(expr) == "(x * x) + (y * 2)"
      assert list(expr.leaf_symbols()) == [x, x, y]
      assert expr.evaluate({"x": 2, "y": 3}) == 10
      expr = x * x
      assert repr(expr) == f"Symbol('x') * Symbol('x')"
  
imports: import pytest
  from nni.mutable.symbol import Symbol, SymbolicExpression
label_desc: Use image node_id 1 for calling a global function with example usage: test_symbol_repr() without return types