docs: def store(self, out, header=""):
          """ Write the properties list to the stream 'out' along
          with the optional 'header' """
  
          if out.mode[0] != 'w':
              raise ValueError('Steam should be opened in write mode!')
  
          try:
              out.write(''.join(('#',header,'\n')))
              # Write timestamp
              tstamp = time.strftime('%a %b %d %H:%M:%S %Z %Y', time.localtime())
              out.write(''.join(('#',tstamp,'\n')))
              # Write properties from the pristine dictionary
              for prop in self._keyorder:
                  if prop in self._origprops:
                      val = self._origprops[prop]
                      out.write(''.join((prop,'=',self.escape(val),'\n')))
  
              out.close()
          except IOError:
              raise