Data.get ignores column argument for multi-symbol data

[jcazalis]

Data.get(column='S') does not behave correctly: the column argument is ignored and it returns the same DataFrame as Data.get().

Minimal repro

import pandas as pd
import vectorbt as vbt

class RandomData(vbt.Data):
    @classmethod
    def download_symbol(cls, symbol, **kwargs):
        index = pd.date_range("2021-01-01", "2021-01-03")
        return pd.Series([1.0, 2.0, 3.0], index=index)  # unnamed Series

rand_data = RandomData.download(["RANDNX1", "RANDNX2"])
print(rand_data.get(column="RANDNX1"))

Output is

symbol                     RANDNX1  RANDNX2
2021-01-01 00:00:00+00:00      1.0      1.0
2021-01-02 00:00:00+00:00      2.0      2.0
2021-01-03 00:00:00+00:00      3.0      3.0

Observed behavior

get(column="RANDNX1") returns the same result as get()

Expected behavior

get(column="RANDNX1") should return only the data for symbol RANDNX1

Cause

It seems to come from the concat method, which doesn't behave properly. concat() returns a dict with None as the only key

rand_data.concat(level_name="RANDNX1")

Output is

{None: RANDNX1                    RANDNX1  RANDNX2
 2021-01-01 00:00:00+00:00      1.0      1.0
 2021-01-02 00:00:00+00:00      2.0      2.0
 2021-01-03 00:00:00+00:00      3.0      3.0}

Environment

vectorbt 0.28.5
Python 3.13.7