firstValidDate()
Signature:
first_valid_time: Optional[numpy.datetime64]
The hec-python-library equivalent of Jython method firstValidDate():
This method is implemented as a property of the TimeSeries class.
The property value will be None if the time series is empty.
Example:
from datetime import datetime
from hec import HecTime, TimeSeries
ts: TimeSeries
dt: Optional[datetime]
if ts.first_valid_time:
dt = ts.HecTime(first_valid_time).datetime()
else:
dt = None