code: def test_global_cache():
      """Test use of the global cache."""
      from sympy.printing.theanocode import global_cache
  
      backup = dict(global_cache)
      try:
          # Temporarily empty global cache
          global_cache.clear()
  
          for s in [x, X, f_t]:
              with warns_deprecated_sympy():
                  st = theano_code(s)
                  assert theano_code(s) is st
  
      finally:
          # Restore global cache
          global_cache.update(backup)
  
imports: import logging
  from sympy.external import import_module
  from sympy.testing.pytest import raises, SKIP, warns_deprecated_sympy
  import sympy
  from sympy.core.singleton import S
  from sympy.abc import x, y, z, t
  from sympy.printing.theanocode import theano_code, dim_handling, theano_function
label_desc: Use image node_id 38 for calling a global function with example usage: test_global_cache() without return types