code: def epscSi(lam: np.ndarray) -> np.ndarray:
      a = np.arange(250, 1500, 5)
      e = np.load(
          Path(__file__).with_name("epsilon_epscSi.npy")
      )  # saved with np.save(filename, e) and dumped in this folder
      y = np.argmin(np.sign(lam - a)) - 1
      epsilon = (e[y + 1] - e[y]) / (a[y + 1] - a[y]) * (
          lam - a[y]
      ) + e[y]
      return epsilon
  
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 10 for calling a global function with example usage: epscSi(lam) and returns: epsilon