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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 is_snp(reference_bases, alternate_bases):
 """ Return whether or not the variant is a SNP """

    if len(reference_bases) > 1:
        return False
    for alt in alternate_bases:
        if alt is None:
            return False
        if alt not in ['A', 'C', 'G', 'T', 'N', '*']:
            return False
    return True