code: def test_checks(self):
      # Test header checks
      hdr_t = self.header_class()
      # _dxer just returns the diagnostics as a string
      # Default hdr is OK
      assert self._dxer(hdr_t) == ""
      # Version should be 1
      hdr = hdr_t.copy()
      hdr["version"] = 2
      assert self._dxer(hdr) == "Unknown MGH format version"
  
imports: import io
  import os
  import pathlib
  import numpy
  import pytest
  from numpy.testing import assert_almost_equal, assert_array_almost_equal, assert_array_equal
  from ...None import imageglobals
  from ...fileholders import FileHolder
  from ...openers import ImageOpener
  from ...spatialimages import HeaderDataError
  from ...testing import data_path
  from ...tests import test_spatialimages
  from ...tests import test_wrapstruct
  from ...tmpdirs import InTemporaryDirectory
  from ...volumeutils import sys_is_le
  from ...wrapstruct import WrapStructError
  from ..None import load, save
  from ..mghformat import MGHError, MGHHeader, MGHImage
label_desc: Use image node_id 9 for calling the TestMGHHeader obj's underlying member method code with example usage: obj.test_checks() without return types