`Series.valueCounts` run into error when all the value are unique

[kikiatproton]

Describe the bug Series.valueCounts run into error when all the value are unique

To Reproduce Steps to reproduce the behavior:

1. Parse a .csv file

dfd.readCSV(file).then((df) => {
    const sf = df[df.columns[0]];
    sf.valueCounts().print();
})

2. See error IndexError: Row index must contain unique values

Expected behavior Should display all valueCount

Screenshots