code: def grow(self, len):
          
          ret = libxml2mod.xmlParserInputBufferGrow(self._o, len)
          return ret
docs: Grow up the content of the input buffer, the old data are
            preserved This routine handle the I18N transcoding to
            internal UTF-8 This routine is used when operating the
            parser in normal (pull) mode  TODO: one should be able to
            remove one extra copy by copying directly onto in->buffer
             or in->raw