Add type annotations for utils

lib/streamlit/elements/utils.py

@@ -31,7 +31,7 @@ def clean_text(text: Any) -> str:
     return textwrap.dedent(str(text)).strip()
 
 
-def last_index_for_melted_dataframes(data):
+def last_index_for_melted_dataframes(data: Any) -> Any:
     if type_util.is_dataframe_compatible(data):
         data = type_util.convert_anything_to_df(data)
 
@@ -55,7 +55,7 @@ def check_callback_rules(
         )
 
 
-_shown_default_value_warning = False
+_shown_default_value_warning: bool = False
 
 
 def check_session_state_rules(

lib/streamlit/util.py

@@ -18,12 +18,13 @@
 import os
 import subprocess
 
-from typing import Any, List
+from typing import Any, Dict, List, TypeVar
+from typing_extensions import Final
 
 from streamlit import env_util
 
 # URL of Streamlit's help page.
-HELP_DOC = "https://docs.streamlit.io/"
+HELP_DOC: Final = "https://docs.streamlit.io/"
 
 
 def memoize(func):
@@ -94,7 +95,7 @@ def _open_browser_with_command(command, url):
         subprocess.Popen(cmd_line, stdout=devnull, stderr=subprocess.STDOUT)
 
 
-def _maybe_tuple_to_list(item):
+def _maybe_tuple_to_list(item: Any) -> Any:
     """Convert a tuple to a list. Leave as is if it's not a tuple."""
     if isinstance(item, tuple):
         return list(item)
@@ -129,7 +130,10 @@ def index_(iterable, x) -> int:
     raise ValueError("{} is not in iterable".format(str(x)))
 
 
-def lower_clean_dict_keys(dict):
+_Value = TypeVar("_Value")
+
+
+def lower_clean_dict_keys(dict: Dict[str, _Value]) -> Dict[str, _Value]:
     return {k.lower().strip(): v for k, v in dict.items()}