diff --git a/openwpm_utils/s3.py b/openwpm_utils/s3.py
index 3e8581c..2242a9e 100644
--- a/openwpm_utils/s3.py
+++ b/openwpm_utils/s3.py
@@ -15,8 +15,8 @@
 from openwpm_utils.dataquality import TableFilter
 
 
-class S3Dataset(object):
-    def __init__(self, s3_directory, s3_bucket="openwpm-crawls"):
+class S3Dataset:
+    def __init__(self, s3_directory: str, s3_bucket: str = "openwpm-crawls"):
         """Helper class to load OpenWPM datasets from S3 using pandas
 
         This dataset wrapper is safe to use by spark worker processes, as it
@@ -87,8 +87,11 @@ def collect_content(self, content_hash, beautify=False):
 
 class PySparkS3Dataset(S3Dataset):
     def __init__(
-        self, spark_context, s3_directory: str, s3_bucket: str = "openwpm-crawls"
-    ):
+        self,
+        spark_context: SparkContext,
+        s3_directory: str,
+        s3_bucket: str = "openwpm-crawls",
+    ) -> None:
         """Helper class to load OpenWPM datasets from S3 using PySpark
 
         Parameters
@@ -111,7 +114,7 @@ def __init__(
 
     def read_table(
         self, table_name: str, columns: List[str] = None, mode: str = "successful"
-    ):
+    ) -> DataFrame:
         """Read `table_name` from OpenWPM dataset into a pyspark dataframe.
 
         Parameters
@@ -126,7 +129,6 @@ def read_table(
             if one of it's commands failed or if it's in the interrupted table
         """
         table = self._sql_context.read.parquet(self._s3_table_loc % table_name)
-
         if mode == "all":
             table = table
         elif mode == "failed":