feedback -> master

.gitignore

@@ -126,3 +126,11 @@ train/
 ssd_mobilenet_v1_coco_2017_11_17/**
 mscoco_label_map.pbtxt
 
+# random video directories
+miris_10/*
+output.mkv
+sample1/*
+sample2/*
+*.txt
+deprecated_files/*
+batch*

deeplens/cache_streams.py

@@ -0,0 +1,64 @@
+import json
+from deeplens.utils.error import MissingIndex
+from deeplens.streams import *
+
+class CacheStream(DataStream):
+    def __init__(self, name, operator):
+        super().__init__(name)
+        self.data = []
+        self.index = 0
+        self.keep_all = False
+        self.operator = operator
+
+    #only used by GraphManager -> to return results 
+    #if you need to keep some datastream, set the results parameter on GraphManager run 
+    def set_keep_all(self):
+        self.keep_all = True
+
+    def add_iter(self, op_name):
+        self.iters[op_name] = -1
+        return self
+
+    def next(self, op_name):
+        if op_name not in self.iters:
+            raise StopIteration()
+        self.iters[op_name] += 1
+        i = self.iters[op_name]
+        while True:
+            if i < self.index:
+                raise MissingIndex('Cache index not saved')
+            if i < self.index + len(self.data):
+                break
+            try:
+                next(self.operator)
+            except StopIteration:
+                del self.iters[op_name]
+                raise StopIteration()
+
+        min_index = min(self.iters.values())
+        if not self.keep_all:
+            if min_index == i:
+                while self.index < i:
+                    self.index += 1
+                    del self.data[0]
+        return self.data[i - self.index]
+
+    def insert(self, value):
+        self.data.append(value)
+
+    def all(self, value):
+        return self.data
+    @staticmethod
+    def init_mat():
+        return []
+
+    @staticmethod
+    def append(data, prev):
+        return prev.append(data)
+
+    @staticmethod
+    def materialize(data, fp = None):
+        if not fp:
+            return json.dumps(data)
+        else:
+            return json.dump(data, fp)