feat: add Consolidator, OverlapConsolidator

Consolidator:
  interface

OverlapConsolidator:
  condenses features if their times overlap

pipeline/consolidators.py

@@ -0,0 +1,59 @@
+"""Consolidators for features extracted from media files"""
+
+from abc import ABC
+
+class Consolidator(ABC):
+    """Consolidator interface.
+
+    A Consolidator's purpose is to reduce a list of features based on eg adjacency/overlap in time.
+
+    Illustration
+    ============
+
+    feature1:
+    <---------->
+    feature2:
+         <------------>
+    consolidated:
+    <----------------->
+
+    TODO: consider how to ensure we only try to merge features from the same path!! #important
+    """
+    def __init__(self, features=None):
+        if features is None or len(features) == 0:
+            raise ValueError("Features must be provided") # TODO: #API -- decide if this is necessary
+        # maybe we want to permit [] which would 'consolidate' to []
+        self.features = features
+
+        def consolidate(self):
+            """Consolidate features by some criterion/criteria (eg overlap, adjacency)"""
+
+
+class OverlapConsolidator(Consolidator):
+    """Consolidator that merges overlapping features.
+
+    An overlap is defined as two features that share a common interval of time,ie:
+      interval1.end < interval2.start or
+      interval2.start < interval1.end
+    """
+
+    def consolidate(self):
+        """Consolidate overlapping features"""
+        # sort features by start time
+        self.features.sort(key=lambda x: x.interval.start)
+
+        # merge overlapping features
+        # TODO: check my working here (or write tests...)
+        consolidated = []
+        current = self.features[0]
+        for feature in self.features[1:]:
+            if current.interval.end < feature.interval.start:
+                # no overlap
+                consolidated.append(current)
+                current = feature
+            else:
+                # overlap
+                current.interval.end = max(current.interval.end, feature.interval.end)
+        consolidated.append(current)
+
+        self.features = consolidated