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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 from_native(cls, regex):
 """Convert a Python regular expression into a ``Regex`` instance. Note that in Python 3, a regular expression compiled from a :class:`str` has the ``re.UNICODE`` flag set. If it is undesirable to store this flag in a BSON regular expression, unset it first:: :Parameters: - `regex`: A regular expression object from ``re.compile()``. .. warning:: Python regular expressions use a different syntax and different set of flags than MongoDB, which uses `PCRE`_. A regular expression retrieved from the server may not compile in Python, or may match a different set of strings in Python than when used in a MongoDB query. .. _PCRE: http://www.pcre.org/ """

        if not isinstance(regex, RE_TYPE):
            raise TypeError(
                "regex must be a compiled regular expression, not %s"
                % type(regex))

        return Regex(regex.pattern, regex.flags)