code: def map_containing(self, address):
          
          page_offset = self._page(address)
          if page_offset not in self._page2map:
              raise MemoryException("Page not mapped", address)
          return self._page2map[page_offset]
docs: Returns the L{MMap} object containing the address.
  
          :param address: the address to obtain its mapping.
          :rtype: L{MMap}
  
          @todo: symbolic address