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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _tidy_names(names, nnames, extra_names=None):
 """Truncate or extend names so that its len is nnames. The list is modified, this function returns nothing. Args: names (list):
 list of names. nnames (int):
 desired number of names. extra_names (list of str):
 list of names to be used to extend the list if needed. If this list isn't provided, a range is used instead. """

    if len(names) < nnames and extra_names is not None:
        names.extend(extra_names)
    names.extend(range(nnames - len(names)))
    del names[nnames:]