code: def test_symbolic_matrix_elements():
      n, m = symbols("n,m")
      s1 = BBra([n])
      s2 = BKet([m])
      o = B(0)
      e = apply_operators(s1 * o * s2)
      assert e == sqrt(m) * KroneckerDelta(n, m - 1)
  
imports: from sympy.physics.secondquant import Dagger, Bd, VarBosonicBasis, BBra, B, BKet, FixedBosonicBasis, matrix_rep, apply_operators, InnerProduct, Commutator, KroneckerDelta, AnnihilateBoson, CreateBoson, BosonicOperator, F, Fd, FKet, BosonState, CreateFermion, AnnihilateFermion, evaluate_deltas, AntiSymmetricTensor, contraction, NO, wicks, PermutationOperator, simplify_index_permutations, _sort_anticommuting_fermions, _get_ordered_dummies, substitute_dummies, FockStateBosonKet, ContractionAppliesOnlyToFermions
  from sympy.concrete.summations import Sum
  from sympy.core.function import Function, expand
  from sympy.core.numbers import I, Rational
  from sympy.core.singleton import S
  from sympy.core.symbol import Dummy, Symbol, symbols
  from sympy.functions.elementary.miscellaneous import sqrt
  from sympy.printing.repr import srepr
  from sympy.simplify.simplify import simplify
  from sympy.testing.pytest import slow, raises
  from sympy.printing.latex import latex
label_desc: Use image node_id 12 for calling a global function with example usage: test_symbolic_matrix_elements() without return types