code: def add_suffix(in_files, suffix):
      
      import os.path as op
      from nipype.utils.filemanip import fname_presuffix, filename_to_list
      return op.basename(fname_presuffix(filename_to_list(in_files)[0],
                                         suffix=suffix))
docs: Wrap nipype's fname_presuffix to conveniently just add a prefix
  
      >>> add_suffix([
      ...     '/path/to/sub-045_ses-test_T1w.nii.gz',
      ...     '/path/to/sub-045_ses-retest_T1w.nii.gz'], '_test')
      'sub-045_ses-test_T1w_test.nii.gz'