class_docstr: Filter used to color mesh faces by a picking ID.
  
  Note that the ID color uses the alpha channel, so this may not be used
  with blending enabled.
  
  Examples
  --------
  :ref:`sphx_glr_gallery_scene_face_picking.py`
class_docstr_tok: ["Filter","used","to","color","mesh","faces","by","a","picking","ID",".","Note","that","the","ID","color","uses","the","alpha","channel",",","so","this","may","not","be","used","with","blending","enabled",".","Examples","--","--","--","--",":","ref",":","`","sphx_glr_gallery_scene_face_picking.py","`"]
code: def _get_picking_ids(self):
      if self._visual.mesh_data.is_empty():
          n_faces = 0
      else:
          n_faces = len(self._visual.mesh_data.get_faces())
  
      # we only care about the number of faces changing
      if self._n_primitives == n_faces:
          return None
      self._n_primitives = n_faces
  
      ids = np.arange(1, n_faces + 1, dtype=np.uint32)
      ids = np.repeat(ids, 3, axis=0)  # repeat id for each vertex
      return ids
  
imports: import numbers
  import numpy
  from vispy.gloo import Texture2D, VertexBuffer
  from vispy.visuals.shaders import Function, Varying
  from vispy.visuals.filters import Filter, PrimitivePickingFilter
  from ...color import Color
label_desc: Use image node_id 1 for calling the FacePickingFilter obj's underlying member method code with example usage: obj._get_picking_ids() and returns: ids, None