Forecast (#3219)

* add forecasting code

* add statsmodel

* sort import

* sort import fix

* fixing black

* sort requirement

* optimize code

* try with limited data

* sort again

* sort fix

* sort fix

* delete warning and black

* add code for forecasting

* use black

* add more hints to describe

* add doctest

* finding whitespace

* fixing doctest

* delete

* revert back

* revert back

* revert back again

* revert back again

* revert back again

* try trimming whitespace

* try adding doctypeand etc

* fixing reviews

* deleting all the space

* fixing the build

* delete x

* add description for safety checker

* deleting subscription integer

* fix docthint

* make def to use function parameters and return values

* make def to use function parameters and return values

* type hints on data safety checker

* optimize code

* Update run.py

Co-authored-by: FVFYK3GEHV22 <fvfyk3gehv22@FVFYK3GEHV22s-MacBook-Pro.local>
Co-authored-by: Christian Clauss <cclauss@me.com>