code: def test_Poisson():
      l = 3
      x = Poisson("x", l)
      assert E(x) == l
      assert E(2 * x) == 2 * l
      assert variance(x) == l
      assert density(x) == PoissonDistribution(l)
      assert isinstance(E(x, evaluate=False), Expectation)
      assert isinstance(E(2 * x, evaluate=False), Expectation)
      # issue 8248
      assert x.pspace.compute_expectation(1) == 1
  
imports: from sympy.concrete.summations import Sum
  from sympy.core.numbers import I, Rational, oo, pi
  from sympy.core.singleton import S
  from sympy.core.symbol import Symbol
  from sympy.functions.elementary.complexes import im, re
  from sympy.functions.elementary.exponential import log
  from sympy.functions.elementary.integers import floor
  from sympy.functions.elementary.miscellaneous import sqrt
  from sympy.functions.elementary.piecewise import Piecewise
  from sympy.functions.special.bessel import besseli
  from sympy.functions.special.beta_functions import beta
  from sympy.functions.special.zeta_functions import zeta
  from sympy.sets.sets import FiniteSet
  from sympy.simplify.simplify import simplify
  from sympy.utilities.lambdify import lambdify
  from sympy.core.relational import Eq, Ne
  from sympy.functions.elementary.exponential import exp
  from sympy.logic.boolalg import Or
  from sympy.sets.fancysets import Range
  from sympy.stats import P, E, variance, density, characteristic_function, where, moment_generating_function, skewness, cdf, kurtosis, coskewness
  from sympy.stats.drv_types import PoissonDistribution, GeometricDistribution, FlorySchulz, Poisson, Geometric, Hermite, Logarithmic, NegativeBinomial, Skellam, YuleSimon, Zeta, DiscreteRV
  from sympy.testing.pytest import slow, nocache_fail, raises
  from sympy.stats.symbolic_probability import Expectation
label_desc: Use image node_id 2 for calling a global function with example usage: test_Poisson() without return types