code: def test_floor_exact_64():
      # float64
      for e in range(53, 63):
          start = np.float64(2**e)
          across = start + np.arange(2048, dtype=np.float64)
          gaps = set(np.diff(across)).difference([0])
          assert len(gaps) == 1
          gap = gaps.pop()
          assert gap == int(gap)
          test_val = 2 ** (e + 1) - 1
          assert floor_exact(test_val, np.float64) == 2 ** (
              e + 1
          ) - int(gap)
  
file_path: nibabel/nibabel/tests/test_floating.py
imports: import sys
  from contextlib import nullcontext
  import numpy
  import pytest
  from packaging.version import Version
  from ..casting import FloatingError, _check_maxexp, _check_nmant, ceil_exact, floor_exact, floor_log2, have_binary128, longdouble_precision_improved, ok_floats, on_powerpc, sctypes, type_info
  from ..testing import suppress_warnings
label_desc: Use image node_id 8 for calling a global function with example usage: test_floor_exact_64() without return types