diff --git a/refresh-certificate.py b/refresh-certificate.py
index 74c85ff..925c55e 100755
--- a/refresh-certificate.py
+++ b/refresh-certificate.py
@@ -39,11 +39,14 @@ import random
 import base64
 from cryptography import x509
 from cryptography.hazmat.primitives.serialization import Encoding
+from dateutil.parser import parse
+from typeguard import typechecked
 
 import requests
 import coloredlogs
 
-def create_nonce(length: int=45):
+@typechecked
+def create_nonce(length: int=45) -> str:
     """
     Generate a random nonce string.
 
@@ -72,7 +75,9 @@ def create_nonce(length: int=45):
 
     return nonce
 
-def get_bearer(hostname: str, verify: bool, username: str, password:str):
+
+@typechecked
+def get_bearer(hostname: str, verify: bool, username: str, password:str) -> str:
     """
     Retrieve an OAuth bearer token for authentication with a HP CDM server.
 
@@ -170,8 +175,10 @@ def get_bearer(hostname: str, verify: bool, username: str, password:str):
 
     return bearer
 
+
+@typechecked
 def get_csr(hostname: str, verify: bool, username: str, password: str, ou: str, org: str, city:str,
-            state: str, country: str, filename: str):
+            state: str, country: str, filename: str) -> None:
     """
     Generate a Certificate Signing Request (CSR) for a HP CDM server.
 
@@ -252,12 +259,16 @@ def get_csr(hostname: str, verify: bool, username: str, password: str, ou: str,
             finished = True
 
     csr = csr['certificateData']
-    print(csr)
+
+    logger.debug('CSR:\n %s', csr)
 
     with open(filename, 'w+', encoding='utf-8') as f:
         f.write(csr)
 
-def install_certificate(hostname, verify, username, password, filename, bearer=None):
+
+@typechecked
+def install_certificate(hostname: str, verify: bool, username: str, password: str, filename:str,
+                        bearer=None) -> None:
     """
     Install a certificate on a HP CDM server.
 
@@ -333,7 +344,10 @@ def install_certificate(hostname, verify, username, password, filename, bearer=N
 
             logger.info('Certificate successfully installed.')
 
-def get_certificates(hostname, verify, username, password, bearer=None):
+
+@typechecked
+def get_certificates(hostname:str, verify:bool, username: str, password: str, 
+                     bearer=None) -> dict[int, dict]:
     """
     Retrieve a list of certificates from an HP CDM server.
 
@@ -386,6 +400,8 @@ def get_certificates(hostname, verify, username, password, bearer=None):
 
     return res
 
+
+@typechecked
 def delete_certificate(hostname, verify, username, password, certificates, certid, bearer=None):
     """
     Delete a certificate from an HP CDM server.