Update Collections_API.md

Author: Roberto De Ioris

docs/Collections_API.md

@@ -5,7 +5,7 @@ The ICollectionManager class exposes methods to manage the assets collections:
 ```python
 from unreal_engine import ICollectionManager
 
-print(ICollectionManager.get_collection())
+print(ICollectionManager.get_collections())
 ```
 
 The api expects knowledge of a bunch of enums mapped as int:
@@ -37,4 +37,21 @@ enum Type
 
 ### get_collections()
 
-returns the list of collections as a tuple with the form (name, ECollectionShareType)
+returns the list of collections as a python list of tuples with the form (name, ECollectionShareType)
+
+### get_root_collections()
+
+returns the list of root collections as a python list of tuples with the form (name, ECollectionShareType)
+
+### get_child_collections(name, ECollectionShareType)
+
+returns the list of child collections for a collection (given as name and type) as a python list of tuples with the form (name, ECollectionShareType)
+
+### get_root_collection_names()
+
+returns the names of root collections as a python list of strings
+
+### get_collection_names()
+
+returns the names of collections as a python list of strings
+