Revert "Make sessions async"

This reverts commit d2de0f3aca.

telethon/sessions/abstract.py

@@ -79,7 +79,7 @@ class Session(ABC):
         raise NotImplementedError
 
     @abstractmethod
-    async def get_update_state(self, entity_id):
+    def get_update_state(self, entity_id):
         """
         Returns the ``UpdateState`` associated with the given `entity_id`.
         If the `entity_id` is 0, it should return the ``UpdateState`` for
@@ -89,7 +89,7 @@ class Session(ABC):
         raise NotImplementedError
 
     @abstractmethod
-    async def set_update_state(self, entity_id, state):
+    def set_update_state(self, entity_id, state):
         """
         Sets the given ``UpdateState`` for the specified `entity_id`, which
         should be 0 if the ``UpdateState`` is the "general" state (and not
@@ -103,15 +103,14 @@ class Session(ABC):
         Returns an iterable over all known pairs of ``(entity ID, update state)``.
         """
 
-    @abstractmethod
-    async def close(self):
+    def close(self):
         """
         Called on client disconnection. Should be used to
         free any used resources. Can be left empty if none.
         """
 
     @abstractmethod
-    async def save(self):
+    def save(self):
         """
         Called whenever important properties change. It should
         make persist the relevant session information to disk.
@@ -119,15 +118,22 @@ class Session(ABC):
         raise NotImplementedError
 
     @abstractmethod
-    async def delete(self):
+    def delete(self):
         """
         Called upon client.log_out(). Should delete the stored
         information from disk since it's not valid anymore.
         """
         raise NotImplementedError
 
+    @classmethod
+    def list_sessions(cls):
+        """
+        Lists available sessions. Not used by the library itself.
+        """
+        return []
+
     @abstractmethod
-    async def process_entities(self, tlo):
+    def process_entities(self, tlo):
         """
         Processes the input ``TLObject`` or ``list`` and saves
         whatever information is relevant (e.g., ID or access hash).
@@ -135,7 +141,7 @@ class Session(ABC):
         raise NotImplementedError
 
     @abstractmethod
-    async def get_input_entity(self, key):
+    def get_input_entity(self, key):
         """
         Turns the given key into an ``InputPeer`` (e.g. ``InputPeerUser``).
         The library uses this method whenever an ``InputPeer`` is needed
@@ -143,3 +149,24 @@ class Session(ABC):
         to use a cached username to avoid extra RPC).
         """
         raise NotImplementedError
+
+    @abstractmethod
+    def cache_file(self, md5_digest, file_size, instance):
+        """
+        Caches the given file information persistently, so that it
+        doesn't need to be re-uploaded in case the file is used again.
+
+        The ``instance`` will be either an ``InputPhoto`` or ``InputDocument``,
+        both with an ``.id`` and ``.access_hash`` attributes.
+        """
+        raise NotImplementedError
+
+    @abstractmethod
+    def get_file(self, md5_digest, file_size, cls):
+        """
+        Returns an instance of ``cls`` if the ``md5_digest`` and ``file_size``
+        match an existing saved record. The class will either be an
+        ``InputPhoto`` or ``InputDocument``, both with two parameters
+        ``id`` and ``access_hash`` in that order.
+        """
+        raise NotImplementedError