code: def zero_symbols(expression):
      return S.Zero if isinstance(expression, Symbol) else expression
  
imports: from sympy.strategies.traverse import top_down, bottom_up, sall, top_down_once, bottom_up_once, basic_fns
  from sympy.strategies.rl import rebuild
  from sympy.strategies.util import expr_fns
  from sympy.core.add import Add
  from sympy.core.basic import Basic
  from sympy.core.numbers import Integer
  from sympy.core.singleton import S
  from sympy.core.symbol import Str, Symbol
  from sympy.abc import x, y, z
label_desc: Use image node_id 1 for calling a global function with example usage: zero_symbols(expression) and returns: unknown