How to use the laspy.header.EVLR function in laspy

if not self.header.version in ("1.3", "1.4"):
            return


        if self.header.version == "1.3":
            if self.header.start_wavefm_data_rec != 0:
                self.seek(self.header.start_wavefm_data_rec, rel = False)
                num_vlrs = 1
            else:
                num_vlrs = 0
        elif self.header.version == "1.4":
            self.seek(self.header.start_first_evlr, rel = False)
            num_vlrs = self.get_header_property("num_evlrs")
        for i in xrange(num_vlrs):
            new_vlr = laspy.header.EVLR(None, None, None)
            new_vlr.build_from_reader(self)
            self.evlrs.append(new_vlr)
        return