code: def arc_id(arc, graph):
      k = graph.n_arcs - arc - 1
      if graph.use_arc_mixing:
          smallv = (k > graph.num_total_big_subsequence_numbers) & 1
          k -= graph.num_total_big_subsequence_numbers * smallv
          subsequence_length2 = graph.subsequence_length - smallv
          subsequence_num = (
              k // subsequence_length2
          ) + graph.num_big_subsequences * smallv
          subsequence_offset = (
              k % subsequence_length2
          ) * graph.mixing_coeff
  
          return subsequence_offset + subsequence_num
      else:
          return k
  
imports: import numpy
  import numba
  from collections import namedtuple
  from enum import Enum, IntEnum
label_desc: Use image node_id 8 for calling a global function with example usage: arc_id(arc, graph) and returns: unknown, k