class_docstr: Class for Cifti2 header extension
class_docstr_tok: ["Class","for","Cifti2","header","extension"]
code: def _chk_qfac(hdr, fix=False):
      # Allow qfac of 0 without complaint for CIFTI-2
      rep = Report(HeaderDataError)
      if hdr["pixdim"][0] in (-1, 0, 1):
          return hdr, rep
      rep.problem_level = 20
      rep.problem_msg = (
          "pixdim[0] (qfac) should be 1 (default) or 0 or -1"
      )
      if fix:
          hdr["pixdim"][0] = 1
          rep.fix_msg = "setting qfac to 1"
      return hdr, rep
  
imports: from io import BytesIO
  import numpy
  from packaging.version import Version, parse
  from ..None import xmlutils
  from ..batteryrunners import Report
  from ..nifti1 import Nifti1Extension, extension_codes, intent_codes
  from ..nifti2 import Nifti2Header, Nifti2Image
  from ..spatialimages import HeaderDataError
  from .cifti2 import CIFTI_BRAIN_STRUCTURES, CIFTI_MODEL_TYPES, Cifti2BrainModel, Cifti2Header, Cifti2HeaderError, Cifti2Label, Cifti2LabelTable, Cifti2Matrix, Cifti2MatrixIndicesMap, Cifti2MetaData, Cifti2NamedMap, Cifti2Parcel, Cifti2Surface, Cifti2TransformationMatrixVoxelIndicesIJKtoXYZ, Cifti2VertexIndices, Cifti2Vertices, Cifti2Volume, Cifti2VoxelIndicesIJK, _underscore
label_desc: Use image node_id 3 for calling the _Cifti2AsNiftiHeader obj's underlying member method code with example usage: obj._chk_qfac(hdr, fix) and returns: hdr,  rep, hdr,  rep