docs: 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