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* Enhanced custom SinkDSM:
* Renamed keyword argument `method` to `approach`
* Renamed approaches `interval` to `oemof` and `delay` to `DIW`
* Added modeling approach `DLR` (PhD thesis of Hans Christian Gils 2015)
* Included load shedding
* Introduced `recovery_time` in `DIW` approach
* Introduced `shift_time` and other parameters for `DLR` approach
* Included investments in DSM
* Normalized keyword arguments `demand`, `capapcity_up` and `capacity_down`
Changelog
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