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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 _ip_string_from_prefix(self, prefixlen=None):
 """Turn a prefix length into a dotted decimal string. Args: prefixlen: An integer, the netmask prefix length. Returns: A string, the dotted decimal netmask string. """

        if not prefixlen:
            prefixlen = self._prefixlen
        return self._string_from_ip_int(self._ip_int_from_prefix(prefixlen))