'Create the database tables.'

def create_tables(self):

    self.con.execute('create    table    imlist(filename)')
    self.con.execute('create    table    imwords(imid,wordid,vocname)')
    self.con.execute('create    table    imhistograms(imid,histogram,vocname)')
    self.con.execute('create    index    im_idx    on    imlist(filename)')
    self.con.execute('create    index    wordid_idx    on    imwords(wordid)')
    self.con.execute('create    index    imid_idx    on    imwords(imid)')
    self.con.execute('create    index    imidhist_idx    on    imhistograms(imid)')
    self.db_commit()
