Plotly - dict对象的值不是JSON可序列化的时间戳？

Question

我尝试使用plotly来创建散点图，但似乎我的时间戳不是JSON可序列化的？这是我得到的错误：

TypeError <built-in method values of dict object at 0x7f6f3d8ac910> is not JSON serializable 

这是我目前的代码：

df = datasets[3]

#New column with hour rounded
df['hour'] = df['p_time'].dt.floor('h')

hour_counts = {}
for hour in df['hour']:
    if hour in hour_counts:
        hour_counts[hour] = hour_counts[hour] + 1
    else:
        hour_counts[hour] = 1 

print hour_counts

count = Scatter(
    x= hour_counts.keys,
    y= hour_counts.values,
    name = "Number of Riders",
    line = dict(color = '#17BECF'),
    opacity = 0.8)

data = [count]

layout = dict(
    title='Time Series with Rangeslider',
    xaxis=dict(
        rangeselector=dict(
            buttons=list([
                dict(count=1,
                     label='1d',
                     step='day',
                     stepmode='backward'),
                dict(count=6,
                     label='6d',
                     step='day',
                     stepmode='backward'),
                dict(step='all')
            ])
        ),
        rangeslider=dict(),
        type='date'
    )
)

fig = dict(data=data, layout=layout)
iplot(fig)

任何人都可以提供一些见解吗？如果这是一个愚蠢的问题，请道歉。我对python很新。谢谢！