code: def levin(ctx, method="levin", variant="u"):
      L = levin_class(method=method, variant=variant)
      L.ctx = ctx
      return L
  
imports: from ..libmp.backend import xrange
  from .calculus import defun
label_desc: Use image node_id 3 for calling a global function with example usage: levin(ctx, method, variant) and returns: L