Get disk space information.

            >>> disk_info = nd.getDiskSpace()

        :return: ``metadata`` if success or ``error message``

        :metadata:
              - expandablespace
              - filemaxsize
              - largefileminsize
              - largefileunusedspace
              - largefileusedspace
              - paymentspace
              - totallargespace
              - totalspace
              - unusedspace
              - usedspace

def getDiskSpace(self):
        """Get disk space information.

            >>> disk_info = nd.getDiskSpace()

        :return: ``metadata`` if success or ``error message``

        :metadata:
              - expandablespace
              - filemaxsize
              - largefileminsize
              - largefileunusedspace
              - largefileusedspace
              - paymentspace
              - totallargespace
              - totalspace
              - unusedspace
              - usedspace
        """
        data = {'userid': self.user_id,
                'useridx': self.useridx,
               }
        s, metadata = self.POST('getDiskSpace',data)

        if s is True:
            usedspace = byte_readable(metadata['usedspace'])
            totalspace = byte_readable(metadata['totalspace'])
            print "Capacity: %s / %s" % (usedspace, totalspace)

            return metadata
        else:
            print message