code: def postprocess_for_cse(expr, optimizations):
      """Postprocess an expression after common subexpression elimination to
      return the expression to canonical SymPy form.
  
      Parameters
      ==========
  
      expr : SymPy expression
          The target expression to transform.
      optimizations : list of (callable, callable) pairs, optional
          The (preprocessor, postprocessor) pairs.  The postprocessors will be
          applied in reversed order to undo the effects of the preprocessors
          correctly.
  
      Returns
      =======
  
      expr : SymPy expression
          The transformed expression.
      """
      for pre, post in reversed(optimizations):
          if post is not None:
              expr = post(expr)
      return expr
  
imports: from collections import defaultdict
  from sympy.core import Basic, Mul, Add, Pow, sympify
  from sympy.core.containers import Tuple, OrderedSet
  from sympy.core.exprtools import factor_terms
  from sympy.core.singleton import S
  from sympy.core.sorting import ordered
  from sympy.core.symbol import symbols, Symbol
  from sympy.matrices import MatrixBase, Matrix, ImmutableMatrix, SparseMatrix, ImmutableSparseMatrix
  from sympy.matrices.expressions import MatrixExpr, MatrixSymbol, MatMul, MatAdd, MatPow, Inverse
  from sympy.matrices.expressions.matexpr import MatrixElement
  from sympy.polys.rootoftools import RootOf
  from sympy.utilities.iterables import numbered_symbols, sift, topological_sort, iterable
  from .None import cse_opts
label_desc: Use image node_id 5 for calling a global function with example usage: postprocess_for_cse(expr, optimizations) and returns: expr