[BUG] Recursive Error in cases where a BDF doesn't have a start and end simultaneously

[victorgarcia98]

Potential recursive error in case that the BeliefDataFrame doesn't have start and end. If start and end are not there, the following properties point to each other.

timely-beliefs/timely_beliefs/beliefs/classes.py

Lines 1117 to 1125 in 31f87c3

	def event_starts(self) -> pd.DatetimeIndex:
	if "event_start" in self.index.names:
	return pd.DatetimeIndex(self.index.get_level_values("event_start"))
	else:
	return pd.DatetimeIndex(
	self.event_ends.to_series(name="event_start").apply(
	lambda event_end: event_end - self.event_resolution
	)
	)

timely-beliefs/timely_beliefs/beliefs/classes.py

Lines 1128 to 1136 in 31f87c3

	def event_ends(self) -> pd.DatetimeIndex:
	if "event_end" in self.index.names:
	return pd.DatetimeIndex(self.index.get_level_values("event_end"))
	else:
	return pd.DatetimeIndex(
	self.event_starts.to_series(name="event_end").apply(
	lambda event_start: event_start + self.event_resolution
	)
	)