docs(remove): add docs for remove_flow()

Author: georgeh0

docs/docs/core/flow_def.mdx

@@ -46,6 +46,22 @@ demo_flow = cocoindex.add_flow_def("DemoFlow", demo_flow_def)
 In both cases, `demo_flow` will be an object with `cocoindex.Flow` class type.
 See [Flow Running](/docs/core/flow_methods) for more details on it.
 
+Sometimes you no longer want to keep states of the flow in memory. We provide a `cocoindex.remove_flow()` method for this purpose:
+
+```python
+cocoindex.remove_flow(demo_flow)
+```
+
+After it's called, `demo_flow` becomes an invalid object, and you should not call any methods of it.
+
+:::note
+
+This only removes states of the flow from the current process, and it won't affect the persistent states.
+
+If you w
+
+:::
+
 </TabItem>
 </Tabs>
 

docs/docs/core/flow_methods.mdx

@@ -100,6 +100,14 @@ cocoindex.drop_all_flows(report_to_stdout=True)
 </TabItem>
 </Tabs>
 
+:::note
+
+After dropping the flow, the in-memory `cocoindex.Flow` instance is still valid, and you can call setup methods on it again.
+
+If you want to remove the flow from the current process, you can call `cocoindex.remove_flow(demo_flow)` to do so (see [related doc](/docs/core/flow_def#entry-point)).
+
+:::
+
 ## Build / update target data
 
 The major goal of a flow is to perform the transformations on source data and build / update data in the target.