code: def backward_eye(n):
      """
      Returns the backward identity matrix of dimensions n x n.
  
      Needed to "turn" the Bezout matrices
      so that the leading coefficients are first.
      See docstring of the function bezout(p, q, x, method='bz').
      """
      M = eye(n)  # identity matrix of order n
  
      for i in range(int(M.rows / 2)):
          M.row_swap(0 + i, M.rows - 1 - i)
  
      return M
  
imports: from sympy.concrete.summations import summation
  from sympy.core.function import expand
  from sympy.core.numbers import nan
  from sympy.core.singleton import S
  from sympy.core.symbol import Dummy
  from sympy.functions.elementary.complexes import Abs, sign
  from sympy.functions.elementary.integers import floor
  from sympy.matrices.dense import eye, Matrix, zeros
  from sympy.printing.pretty.pretty import pretty_print
  from sympy.simplify.simplify import simplify
  from sympy.polys.domains import QQ
  from sympy.polys.polytools import degree, LC, Poly, pquo, quo, prem, rem
  from sympy.polys.polyerrors import PolynomialError
label_desc: Use image node_id 10 for calling a global function with example usage: backward_eye(n) and returns: M