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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 add_modifier(self, m_type=XenaModifierType.standard, **kwargs):
 """ Add modifier. :param m_type: modifier type - standard or extended. :type: xenamanager.xena_stram.ModifierType :return: newly created modifier. :rtype: xenamanager.xena_stream.XenaModifier """


        if m_type == XenaModifierType.standard:
            modifier = XenaModifier(self, index='{}/{}'.format(self.index, len(self.modifiers)))
        else:
            modifier = XenaXModifier(self, index='{}/{}'.format(self.index, len(self.xmodifiers)))
        modifier._create()
        modifier.get()
        modifier.set(**kwargs)
        return modifier