code: def cascade2(A: np.ndarray, B: np.ndarray) -> np.ndarray:
      """
      This function takes two 2x2 matrices A and B, that are assumed to be scattering matrices
      and combines them assuming A is the "upper" one, and B the "lower" one, physically.
      The result is a 2x2 scattering matrix.
      """
      t = 1 / (1 - B[0, 0] * A[1, 1])
      S = np.zeros((2, 2), dtype=complex)
      S[0, 0] = A[0, 0] + A[0, 1] * B[0, 0] * A[1, 0] * t
      S[0, 1] = A[0, 1] * B[0, 1] * t
      S[1, 0] = B[1, 0] * A[1, 0] * t
      S[1, 1] = B[1, 1] + A[1, 1] * B[0, 1] * B[1, 0] * t
      return S
  
file_path: nevergrad/nevergrad/functions/photonics/photonics.py
imports: import typing
  from pathlib import Path
  import numpy
  from scipy.linalg import toeplitz
label_desc: Use image node_id 11 for calling a global function with example usage: cascade2(A, B) and returns: S