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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 setPrefix(self, p, u=None):
 """ Set the element namespace prefix. @param p: A new prefix for the element. @type p: basestring @param u: A namespace URI to be mapped to the prefix. @type u: basestring @return: self @rtype: L{Element} """

        self.prefix = p
        if p is not None and u is not None:
            self.addPrefix(p, u)
        return self