Set the index for the search. If called empty it will remove all information.

        Example:

            s = Search()
            s = s.index('twitter-2015.01.01', 'twitter-2015.01.02')
            s = s.index(['twitter-2015.01.01', 'twitter-2015.01.02'])

def index(self, *index):
        """
        Set the index for the search. If called empty it will remove all information.

        Example:

            s = Search()
            s = s.index('twitter-2015.01.01', 'twitter-2015.01.02')
            s = s.index(['twitter-2015.01.01', 'twitter-2015.01.02'])
        """
        # .index() resets
        s = self._clone()
        if not index:
            s._index = None
        else:
            indexes = []
            for i in index:
                if isinstance(i, string_types):
                    indexes.append(i)
                elif isinstance(i, list):
                    indexes += i
                elif isinstance(i, tuple):
                    indexes += list(i)

            s._index = (self._index or []) + indexes

        return s