code: def test_grouper() -> None:
      output = list(tools.grouper("ABCDEFG", 3, "x"))
      testing.printed_assert_equal(
          output, [list(x) for x in ["ABC", "DEF", "Gxx"]]
      )
  
file_path: nevergrad/nevergrad/common/test_tools.py
imports: import os
  import typing
  import numpy
  from .None import tools
  from .None import testing
label_desc: Use image node_id 3 for calling a global function with example usage: test_grouper() without return types