[ENH] How can I vary loss development factors by year?

[BenL-github]

Is your feature request related to a problem? Please describe. For development constant, how can I vary the loss development factors by year? I would like to know how to do this so the ultimate values vary based on a different loss development pattern by year.

The current docs has this snippet of code

patterns={12: 2, 24: 1.25, 36: 1.1, 48: 1.08, 60: 1.05, 72: 1.02, 84: 1.0, 96: 1.0, 108: 1.0}
cl.DevelopmentConstant(patterns=patterns, style='ldf').fit(triangle).ldf_

	12-Ult	24-Ult	36-Ult	48-Ult	60-Ult	72-Ult	84-Ult	96-Ult	108-Ult
(ALL)	2.0000	1.2500	1.1000	1.0800	1.0500	1.0200	1.0000	1.0000	1.0000

This is the pattern I would like to create:

	12-Ult	24-Ult	36-Ult	48-Ult	60-Ult	72-Ult	84-Ult	96-Ult	108-Ult
2010									1.0000
2011								1.0070	1.0000
2012							1.4000	1.0000	1.0400
2013						1.0200	1.5000	1.0600	1.0000
...	...	...	...	...	...	...	...	...	...
2019	1.0000	1.0700	1.1000	1.0800	1.0500	1.0200	1.5000	1.0600	1.0000

Is your feature request at odds with the scope of the package? No

Describe the solution you'd like Written code example of how I can resolve my issue, or a link to documentation that has an example of how I can do it.

Describe alternatives you've considered Reading documentation