code: def sph2cart(az, el, r) -> tuple:
      """Transform spherical to Cartesian coordinates"""
      rcos_theta = r * cos(el)
      x = rcos_theta * cos(az)
      y = rcos_theta * sin(az)
      z = r * sin(el)
      return x, y, z
  
file_path: pymap3d/src/pymap3d/utils.py
imports: from __future__ import annotations
  from math import pi
  from .ellipsoid import Ellipsoid
  from .mathfun import atan2, cos, hypot, radians, sin
label_desc: Use image node_id 4 for calling a global function with example usage: sph2cart(az, el, r) and returns: x,  y,  z