code: def _get_als_coords_from_chs(chs, drop_chs=None):
      """Extract channel locations in ALS format (x, y, z) from a chs instance.
  
      Returns
      -------
      None if no valid coordinates are found (all zeros)
      """
      if drop_chs is None:
          drop_chs = []
      cart_coords = np.array(
          [d["loc"][:3] for d in chs if d["ch_name"] not in drop_chs]
      )
      if cart_coords.any():  # has coordinates
          # (-y x z) to (x y z)
          cart_coords[:, 0] = -cart_coords[:, 0]  # -y to y
          # swap x (1) and y (0)
          cart_coords[:, [0, 1]] = cart_coords[:, [1, 0]]
      else:
          cart_coords = None
      return cart_coords
  
imports: import numpy
  from ..utils import _check_eeglabio_installed
  import eeglabio.epochs
  import eeglabio.raw
label_desc: Use image node_id 3 for calling a global function with example usage: _get_als_coords_from_chs(chs, drop_chs) and returns: cart_coords