code: def cart2sph(x, y, z) -> tuple:
      """Transform Cartesian to spherical coordinates"""
      hxy = hypot(x, y)
      r = hypot(hxy, z)
      el = atan2(z, hxy)
      az = atan2(y, x)
      return az, el, r
  
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 3 for calling a global function with example usage: cart2sph(x, y, z) and returns: az,  el,  r