Generate a datetime series with same weekday number.
        
        ISO weekday number: Mon = 1, Sun = 7
        
        Usage::
        
            >>> timewrapper.weekday_series( # All Tuesday
            >>>     "2014-01-01 06:30:25", "2014-02-01 06:30:25", weekday=2),
            [
                datetime(2014, 1, 7, 6, 30, 25), 
                datetime(2014, 1, 14, 6, 30, 25),
                datetime(2014, 1, 21, 6, 30, 25),
                datetime(2014, 1, 28, 6, 30, 25),
            ]
        
        **中文文档**
        
        生成星期数一致的时间序列。

def weekday_series(self, start, end, weekday):
        """Generate a datetime series with same weekday number.
        
        ISO weekday number: Mon = 1, Sun = 7
        
        Usage::
        
            >>> timewrapper.weekday_series( # All Tuesday
            >>>     "2014-01-01 06:30:25", "2014-02-01 06:30:25", weekday=2),
            [
                datetime(2014, 1, 7, 6, 30, 25), 
                datetime(2014, 1, 14, 6, 30, 25),
                datetime(2014, 1, 21, 6, 30, 25),
                datetime(2014, 1, 28, 6, 30, 25),
            ]
        
        **中文文档**
        
        生成星期数一致的时间序列。
        """
        startdatetime = self.parse_datetime(start)
        enddatetime = self.parse_datetime(end)
        
        series = list()
        for i in self.dtime_range(startdatetime, enddatetime, freq="1day"):
            if i.isoweekday() == weekday:
                series.append(i)
                
        return series