code: def _persp_transformation(zfront, zback, focal_length):
      e = focal_length
      a = 1  # aspect ratio
      b = (zfront + zback) / (zfront - zback)
      c = -2 * (zfront * zback) / (zfront - zback)
      proj_matrix = np.array(
          [[e, 0, 0, 0], [0, e / a, 0, 0], [0, 0, b, c], [0, 0, -1, 0]]
      )
      return proj_matrix
  
imports: import numpy
  from matplotlib import _api
label_desc: Use image node_id 8 for calling a global function with example usage: _persp_transformation(zfront, zback, focal_length) and returns: proj_matrix