Initializes the database if use_db is True. If the model source is a
file, seralizes the forecast into a HDF5 file. If source is a
generating function or code, creates an empty DB
Parameters:
dbpath (str) – Path to drop the HDF5 database. Defaults to same path
replaced with an hdf5 extension
force (bool) – Forces the serialization even if the DB already
exists