code: def free_symbols(self) -> Set[sympy.Symbol]:
      return set(self.var_to_val.keys()) - set(self.replacements.keys())
  
imports: import functools
  import itertools
  import logging
  from typing import Any, Callable, Dict, Iterable, List, Optional, Set, Tuple, Union
  import sympy
  from sympy import Expr
  from torch.fx.experimental.symbolic_shapes import ShapeEnv
  from torch.utils._sympy.functions import FloorDiv, ModularIndexing
  from torch.utils._sympy.value_ranges import bound_sympy
  from .utils import sympy_subs, sympy_symbol, VarRanges
  from .virtualized import V
label_desc: Use image node_id 35 for calling the SizeVarAllocator obj's underlying member method code with example usage: obj.free_symbols() and returns: unknown