old_contents: from nipype.interfaces.base import (traits,
                                      BaseInterfaceInputSpec, TraitedSpec, BaseInterface,
                                      InputMultiPath, OutputMultiPath, Directory, File)
  from qidicom import hierarchy
  
  
  class GroupDicomInputSpec(BaseInterfaceInputSpec):
      tag = traits.String(mandatory=True)
      
      in_files = InputMultiPath(
          traits.Either(File(exists=True), Directory(exists=True)),
          mandatory=True, desc='The DICOM files to group')
  
  
  class GroupDicomOutputSpec(TraitedSpec):
      series_files_dict = traits.Dict(desc='The series number: [DICOM files] dictionary')
  
  
  class GroupDicom(BaseInterface):
      input_spec = GroupDicomInputSpec
  
      output_spec = GroupDicomOutputSpec
  
      def _run_interface(self, runtime):
          self.grp_dict = hierarchy.group_by(self.inputs.tag, *self.inputs.in_files)
          return runtime
  
      def _list_outputs(self):
          outputs = self._outputs().get()
          outputs['series_files_dict'] = self.grp_dict
          return outputs
  
new_contents: from nipype.interfaces.base import (traits,
                                      BaseInterfaceInputSpec, TraitedSpec, BaseInterface,
                                      InputMultiPath, OutputMultiPath, Directory, File)
  from qidicom import hierarchy
  
  
  class GroupDicomInputSpec(BaseInterfaceInputSpec):
      tag = traits.String(mandatory=True)
      
      in_files = InputMultiPath(
          traits.Either(File(exists=True), Directory(exists=True)),
          mandatory=True, desc='The DICOM files to group')
  
  
  class GroupDicomOutputSpec(TraitedSpec):
      groups = traits.Dict(
          desc='The {tag value: [DICOM files]} dictionary'
      )
  
  
  class GroupDicom(BaseInterface):
      input_spec = GroupDicomInputSpec
  
      output_spec = GroupDicomOutputSpec
  
      def _run_interface(self, runtime):
          self.grp_dict = hierarchy.group_by(self.inputs.tag, *self.inputs.in_files)
          return runtime
  
      def _list_outputs(self):
          outputs = self._outputs().get()
          outputs['groups'] = self.grp_dict
          return outputs
  
subject: Change group variable name.