def copy_files(in_files, out_files):
    """
    Create a function to copy a file that can be modified by a following node
    without changing the original file
    """
    import shutil
    import sys
    if len(in_files) != len(out_files):
        print(
            'ERROR: Length of input files must be identical to the length of '
             + 'outrput files to be copied')
        sys.exit(-1)
    for i, in_file in enumerate(in_files):
        out_file = out_files[i]
        print('copying {0} to {1}'.format(in_file, out_file))
        shutil.copy(in_file, out_file)
    return out_files
