NaN Error in creating a series with dict
```python
import pandas as pd
pd.Series(data={"a":[1,2,3,3,5]}, index=[1,2,3,4,5])

```
#### Problem description
If I use the code above, the output is like this.
```
1   NaN
2   NaN
3   NaN
4   NaN
5   NaN
dtype: float64
```
According to the [document](https://pandas.pydata.org/pandas-docs/stable/generated/pandas.Series.html),it says data could be dict, but actually, if I use dict, the data in Series object will be NaN.

I don't know why ? Is the way I proposed above to create a series is illegal?
