def getScan(self, title, peptide=None):
        """
        allows random lookup
        """
        if self.ra.has_key(title):
            self.filename.seek(self.ra[title][0],0)
            toRead = self.ra[title][1]-self.ra[title][0]
            info = self.filename.read(toRead)
            scan = self.parseScan(info)
        else:
            return None
        return scan
allows random lookup