code: def shepp_logan_phantom():
      """Shepp Logan Phantom.
  
      References
      ----------
      .. [1] L. A. Shepp and B. F. Logan, "The Fourier reconstruction of a head
             section," in IEEE Transactions on Nuclear Science, vol. 21,
             no. 3, pp. 21-43, June 1974. :DOI:`10.1109/TNS.1974.6499235`
  
      Returns
      -------
      phantom : (400, 400) float64 image
          Image of the Shepp-Logan phantom in grayscale.
      """
      return _load("data/phantom.png", as_gray=True)
  
imports: import numpy
  import shutil
  from ..util.dtype import img_as_bool
  from ._registry import registry, registry_urls
  from ..None import __version__
  import os.path
  import os
label_desc: Use image node_id 34 for calling a global function with example usage: shepp_logan_phantom() and returns: _load