Rewrite introduction documentation

examples/session_handling.py

@@ -0,0 +1,42 @@
+# TODO: Consider adding Session.from_file and Session.to_file,
+# which would make this example a lot easier!
+
+import atexit
+import json
+import getpass
+import fbchat
+
+
+def load_cookies(filename):
+    try:
+        # Load cookies from file
+        with open(filename) as f:
+            return json.load(f)
+    except FileNotFoundError:
+        return  # No cookies yet
+
+
+def save_cookies(filename, cookies):
+    with open(filename, "w") as f:
+        json.dump(f, cookies)
+
+
+def load_session(cookies):
+    if not cookies:
+        return
+    try:
+        return fbchat.Session.from_cookies(cookies)
+    except fbchat.FacebookError:
+        return  # Failed loading from cookies
+
+
+cookies = load_cookies("session.json")
+session = load_session(cookies)
+if not session:
+    # Session could not be loaded, login instead!
+    session = fbchat.Session.login("<email>", getpass.getpass())
+
+# Save session cookies to file when the program exits
+atexit.register(lambda: save_cookies("session.json", session.get_cookies()))
+
+# Do stuff with session here