code: def test_pl_true():
      A, B, C = symbols("A,B,C")
      assert pl_true(True) is True
      assert pl_true(A & B, {A: True, B: True}) is True
      assert pl_true(A | B, {A: True}) is True
      assert pl_true(A | B, {B: True}) is True
      assert pl_true(A | B, {A: None, B: True}) is True
      assert pl_true(A >> B, {A: False}) is True
      assert pl_true(A | B | ~C, {A: False, B: True, C: True}) is True
      assert pl_true(Equivalent(A, B), {A: False, B: False}) is True
  
      # test for false
      assert pl_true(False) is False
      assert pl_true(A & B, {A: False, B: False}) is False
      assert pl_true(A & B, {A: False}) is False
      assert pl_true(A & B, {B: False}) is False
      assert pl_true(A | B, {A: False, B: False}) is False
  
      # test for None
      assert pl_true(B, {B: None}) is None
      assert pl_true(A & B, {A: True, B: None}) is None
      assert pl_true(A >> B, {A: True, B: None}) is None
      assert pl_true(Equivalent(A, B), {A: None}) is None
      assert pl_true(Equivalent(A, B), {A: True, B: None}) is None
  
      # Test for deep
      assert pl_true(A | B, {A: False}, deep=True) is None
      assert pl_true(~A & ~B, {A: False}, deep=True) is None
      assert pl_true(A | B, {A: False, B: False}, deep=True) is False
      assert pl_true(A & B & (~A | ~B), {A: True}, deep=True) is False
      assert pl_true((C >> A) >> (B >> A), {C: True}, deep=True) is True
  
imports: from sympy.assumptions.ask import Q
  from sympy.core.symbol import symbols
  from sympy.core.relational import Unequality
  from sympy.logic.boolalg import And, Or, Implies, Equivalent, true, false
  from sympy.logic.inference import literal_symbol, pl_true, satisfiable, valid, entails, PropKB
  from sympy.logic.algorithms.dpll import dpll, dpll_satisfiable, find_pure_symbol, find_unit_clause, unit_propagate, find_pure_symbol_int_repr, find_unit_clause_int_repr, unit_propagate_int_repr
  from sympy.logic.algorithms.dpll2 import dpll_satisfiable
  from sympy.logic.algorithms.z3_wrapper import z3_satisfiable
  from sympy.assumptions.cnf import CNF, EncodedCNF
  from sympy.logic.tests.test_lra_theory import make_random_problem
  from sympy.core.random import randint
  from sympy.testing.pytest import raises, skip
  from sympy.external import import_module
label_desc: Use image node_id 15 for calling a global function with example usage: test_pl_true() without return types