code: def once(self, start, end):
      # cache python dictionary lookups
      dst = self.array
      srca = self.a.array
      srcb = self.b.array
      cond = self.cond.array
  
      for i in range(start, end):
          dst[i] = srca[i] if cond[i] else srcb[i]
  
imports: from __future__ import absolute_import, division, print_function, unicode_literals
  import functools
  import math
  from .linebuffer import LineActions
  from .utils.py3 import cmp, range
label_desc: Use image node_id 3 for calling the If obj's underlying member method code with example usage: obj.once(start, end) without return types