import pandas as pd


def to_pandas(instance: dict, freq: str = None) -> pd.Series:
    """
    Transform a dictionary into a pandas.Series object, using its
    "start" and "target" fields.

    Parameters
    ----------
    instance
        Dictionary containing the time series data.
    freq
        Frequency to use in the pandas.Series index.

    Returns
    -------
    pandas.Series
        Pandas time series object.
    """
    target = instance["target"]
    start = instance["start"]
    if not freq:
        freq = start.freqstr
    index = pd.date_range(start=start, periods=len(target), freq=freq)
    return pd.Series(target, index=index)