'Add a highlight field.
The Search object will be returned, so calls to this can be chained.'

def add_highlight(self, field, fragment_size=None, number_of_fragments=None, fragment_offset=None, type=None):

    if (self._highlight is None):
        self._highlight = HighLighter('<b>', '</b>')
    self._highlight.add_field(field, fragment_size, number_of_fragments, fragment_offset, type=type)
    return self
