code: def test_general_init(self):
      hdr = self.header_class()
      # binaryblock has length given by header data dtype
      binblock = hdr.binaryblock
      assert len(binblock) == hdr.structarr.dtype.itemsize
      # Endianness will always be big, and cannot be set
      assert hdr.endianness == ">"
      # You can also pass in a check flag, without data this has no
      # effect
      hdr = self.header_class(check=False)
  
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 3 for calling the TestMGHHeader obj's underlying member method code with example usage: obj.test_general_init() without return types