Avoid relying on .__iter__ to tell iterators apart

.send_file() would fail with stream objects (those from open())
since they are iterable, and asserting that they weren't bytes
or str was not enough.

telethon/utils.py

@@ -5,6 +5,7 @@ to convert between an entity like an User, Chat, etc. into its Input version)
 import math
 import mimetypes
 import re
+import types
 from mimetypes import add_type, guess_extension
 
 from .tl.types import (
@@ -341,6 +342,17 @@ def is_video(file):
             (mimetypes.guess_type(file)[0] or '').startswith('video/'))
 
 
+def is_list_like(obj):
+    """
+    Returns True if the given object looks like a list.
+
+    Checking if hasattr(obj, '__iter__') and ignoring str/bytes is not
+    enough. Things like open() are also iterable (and probably many
+    other things), so just support the commonly known list-like objects.
+    """
+    return isinstance(obj, (list, tuple, set, dict, types.GeneratorType))
+
+
 def parse_phone(phone):
     """Parses the given phone, or returns None if it's invalid"""
     if isinstance(phone, int):