code: def _parse_inputs(self, skip=None):
      if skip is None:
          skip = []
  
      try:
          if isdefined(self.inputs.grad_file) or isdefined(
              self.inputs.grad_fsl
          ):
              skip += ["in_bvec", "in_bval"]
  
          is_bvec = isdefined(self.inputs.in_bvec)
          is_bval = isdefined(self.inputs.in_bval)
          if is_bvec or is_bval:
              if not is_bvec or not is_bval:
                  raise RuntimeError(
                      "If using bvecs and bvals inputs, both should be defined"
                  )
              skip += ["in_bval"]
      except AttributeError:
          pass
  
      return super()._parse_inputs(skip=skip)
  
file_path: nipype/nipype/interfaces/mrtrix3/base.py
imports: from looseversion import LooseVersion
  from ...None import logging
  from ...utils.filemanip import which
  from ..base import CommandLineInputSpec, CommandLine, traits, File, isdefined, PackageInfo
label_desc: Use image node_id 2 for calling the MRTrix3Base obj's underlying member method code with example usage: obj._parse_inputs(skip) and returns: super