code: def mapper(keys):
      return {int(k): int(v) for v, k in enumerate(keys)}
  
file_path: thinc/thinc/tests/layers/test_mappers.py
imports: import numpy
  import pytest
  from thinc.layers import premap_ids, remap_ids, remap_ids_v2
label_desc: Use image node_id 2 for calling a global function with example usage: mapper(keys) and returns: unknown