def close
    @pstmts.each do |typ, hash|
      hash.each do |sql, pstmt|
        pstmt.close if pstmt
      end
      @pstmts[typ] = {}
    end
  end
def close
    @pstmts.each do |typ, hash|
      hash.each do |sql, pstmt|
        pstmt.close if pstmt
      end
      @pstmts[typ] = {}
    end
  end
Closes the prepared statements
 @since 0.5.0