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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 unstage_signature(vcs, signature):
 """Remove `signature` from the list of staged signatures Args: vcs (easyci.vcs.base.Vcs) signature (basestring) Raises: NotStagedError """

    evidence_path = _get_staged_history_path(vcs)
    staged = get_staged_signatures(vcs)
    if signature not in staged:
        raise NotStagedError
    staged.remove(signature)
    string = '\n'.join(staged)
    with open(evidence_path, 'w') as f:
        f.write(string)