diff --git a/proxylist/metrics.py b/proxylist/metrics.py
index b0c29a4..6d1a045 100644
--- a/proxylist/metrics.py
+++ b/proxylist/metrics.py
@@ -18,5 +18,5 @@ def collect(self):
         )
 
 
-def register_metrics():
+def register_metrics() -> None:
     REGISTRY.register(CustomCollector())
diff --git a/proxylist/models.py b/proxylist/models.py
index ad4b2f3..706573b 100644
--- a/proxylist/models.py
+++ b/proxylist/models.py
@@ -13,7 +13,7 @@
 from proxylist.proxy import update_proxy_status, get_proxy_location
 
 
-def validate_sip002(value):
+def validate_sip002(value) -> None:
     if get_sip002(value) == "":
         raise ValidationError(
             "The value entered is not SIP002 compatible",
@@ -21,7 +21,7 @@ def validate_sip002(value):
         )
 
 
-def validate_not_existing(value):
+def validate_not_existing(value) -> None:
     if Proxy.objects.filter(url=get_sip002(value)):
         raise ValidationError(
             "This proxy was already imported",
@@ -29,7 +29,7 @@ def validate_not_existing(value):
         )
 
 
-def validate_proxy_can_connect(value):
+def validate_proxy_can_connect(value) -> None:
     location = get_proxy_location(get_sip002(value))
     if location is None or location == "unknown":
         raise ValidationError(
@@ -38,7 +38,7 @@ def validate_proxy_can_connect(value):
         )
 
 
-def proxy_validator(value):
+def proxy_validator(value) -> None:
     validate_sip002(value)
     validate_not_existing(value)
     validate_proxy_can_connect(value)
@@ -118,7 +118,7 @@ def update_url_and_location_after_save(sender, instance, created, **kwargs):
 
 
 @receiver(post_save, sender=Proxy)
-def clear_cache(sender, instance, **kwargs):
+def clear_cache(sender, instance, **kwargs) -> None:
     cache.clear()
 
 
diff --git a/proxylist/proxy.py b/proxylist/proxy.py
index ec5f70d..9e4b370 100644
--- a/proxylist/proxy.py
+++ b/proxylist/proxy.py
@@ -20,7 +20,7 @@ def get_proxy_location(proxy_url):
     return output
 
 
-def update_proxy_status(proxy):
+def update_proxy_status(proxy) -> None:
     ip_information = get_proxy_location(proxy_url=proxy.url)
 
     if ip_information:
diff --git a/proxylist/tasks.py b/proxylist/tasks.py
index 2265395..f733ee1 100644
--- a/proxylist/tasks.py
+++ b/proxylist/tasks.py
@@ -23,21 +23,21 @@
 
 
 @db_periodic_task(crontab(minute="15", hour="10"))
-def remove_low_quality_proxies_scheduled():
+def remove_low_quality_proxies_scheduled() -> None:
     remove_low_quality_proxies()
 
 
 @db_periodic_task(crontab(minute="*/20"))
-def update_status_scheduled():
+def update_status_scheduled() -> None:
     update_status()
 
 
 @db_periodic_task(crontab(minute="0"))
-def poll_subscriptions_scheduled():
+def poll_subscriptions_scheduled() -> None:
     poll_subscriptions()
 
 
-def remove_low_quality_proxies():
+def remove_low_quality_proxies() -> None:
     log.info(
         "Removing low quality proxies",
         extra={"task": inspect.currentframe().f_back.f_code.co_name},
@@ -129,7 +129,7 @@ def decode_line(line):
         )
 
 
-def poll_subscriptions():
+def poll_subscriptions() -> None:
     log.info(
         "Started polling subscriptions",
         extra={"task": inspect.currentframe().f_code.co_name},
@@ -282,7 +282,7 @@ def process_line(line, all_urls):
         return proxy
 
 
-def flatten(something):
+def flatten(something) -> None:
     if isinstance(something, (list, tuple, set, range)):
         for sub in something:
             yield from flatten(sub)