code: def _mangle(self, value):
      if not isinstance(value, Cifti2Header):
          raise ValueError("Can only mangle a Cifti2Header.")
      return value.to_xml()
  
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 Cifti2Extension obj's underlying member method code with example usage: obj._mangle(value) and returns: value