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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 _get_zeropoint(expnum, ccd, prefix=None, version='p'):
 """ Retrieve the zeropoint stored in the tags associated with this image. @param expnum: Exposure number @param ccd: ccd of the exposure @param prefix: possible prefix (such as 'fk') @param version: which version: p, s, or o ? @return: zeropoint """

    if prefix is not None:
        DeprecationWarning("Prefix is no longer used here as the 'fk' and 's' have the same zeropoint.")

    key = "zeropoint_{:1s}{:02d}".format(version, int(ccd))
    return get_tag(expnum, key)