def _resample_event_obs(obs, fx, obs_data):
    """
    Resample the event observation.

    Parameters
    ----------
    obs : datamodel.Observation
        The Observation being resampled.
    fx : datamodel.EventForecast
        The corresponding Forecast.
    obs_data : pd.Series
        Timeseries data of the event observation.

    Returns
    -------
    obs_resampled : pandas.Series
        Timeseries data of the Observation resampled to match the Forecast.

    Raises
    ------
    RuntimeError
        If the Forecast and Observation do not have the same interval length.

    """

    if fx.interval_length != obs.interval_length:
        raise ValueError("Event observation and forecast time-series "
                         "must have matching interval length.")
    else:
        obs_resampled = obs_data

    return obs_resampled