Add density estimator and relative extrema finder to preprocessing request.

cml/shared/request.py

 from dataclasses import dataclass
+from typing import Callable, Iterable
 
 from cml.ports.source_adapters import Adapter
+from cml.ports.scikit_adapter import MachineLearningModel
 from cml.domain.reconstruction import Reconstructor
 from cml.domain.data_source import DataSource
 from cml.domain.construction import Constructor
 from cml.shared.settings import (
     PreprocessingSettings,
     BlockProcessingSettings,
-    DeconstructionSettings
+    DeconstructionSettings,
+    ConstructionSettings
 )
 
 
@@ -16,6 +19,8 @@ class PreprocessRequest:
     source_adapter: Adapter
     pre_settings: PreprocessingSettings
     block_settings: BlockProcessingSettings
+    density_estimator: MachineLearningModel
+    relative_extrema: Callable
 
 
 @dataclass