firstValidValue()
Signature:
first_valid_value: Optional[float]
The hec-python-library equivalent of Jython method firstValidValue():
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 hec import TimeSeries
ts: TimeSeries
val: Optional[float]
val = ts.first_valid_value