code: def index(self, columnnames, sort=True):
          
          from .tableindex import tableindex
          return tableindex(self, columnnames, sort)
docs: Return a tableindex object.
  
          :class:`tableindex` lets one get the row numbers of the rows holding
          given values for the columns for which the index is created.
          It uses an in-memory index on which a binary search is done.
          By default the table is sorted on the given columns to get the correct
          index order.
  
          For example::
  
            t = table('3c343.MS')
            tinx = t.index('ANTENNA1')
            print tinx.rownumbers(0)       # print rownrs containing ANTENNA1=0