code: def test_expand():
      assert (2 ** (-1 - x)).expand() == S.Half * 2 ** (-x)
  
imports: from sympy.core import Basic, Rational, Symbol, S, Float, Integer, Mul, Number, Pow, Expr, I, nan, pi, symbols, oo, zoo, N
  from sympy.core.parameters import global_parameters
  from sympy.core.tests.test_evalf import NS
  from sympy.core.function import expand_multinomial
  from sympy.functions.elementary.miscellaneous import sqrt, cbrt
  from sympy.functions.elementary.exponential import exp, log
  from sympy.functions.special.error_functions import erf
  from sympy.functions.elementary.trigonometric import sin, cos, tan, sec, csc, atan
  from sympy.functions.elementary.hyperbolic import cosh, sinh, tanh
  from sympy.polys import Poly
  from sympy.series.order import O
  from sympy.sets import FiniteSet
  from sympy.core.power import power
  from sympy.core.intfunc import integer_nthroot
  from sympy.testing.pytest import warns, _both_exp_pow
  from sympy.utilities.exceptions import SymPyDeprecationWarning
  from sympy.abc import a, b, c, x, y
label_desc: Use image node_id 4 for calling a global function with example usage: test_expand() without return types