df.info() missing space in memory usage
```
In [7]: df = pd.DataFrame({'a': [1, 2], 'b': [3, 4]})

In [8]: df.info()
<class 'pandas.core.frame.DataFrame'>
RangeIndex: 2 entries, 0 to 1
Data columns (total 2 columns):
a    2 non-null int64
b    2 non-null int64
dtypes: int64(2)
memory usage: 112.0bytes
```