diff --git a/waybackpy/cdx_api.py b/waybackpy/cdx_api.py
index 73515a9..7acad0b 100644
--- a/waybackpy/cdx_api.py
+++ b/waybackpy/cdx_api.py
@@ -26,27 +26,25 @@ class WaybackMachineCDXServerAPI(object):
         user_agent: str = DEFAULT_USER_AGENT,
         start_timestamp: Optional[str] = None,
         end_timestamp: Optional[str] = None,
-        filters: List[str] = [],
+        filters: Optional[List[str]] = None,
         match_type: Optional[str] = None,
         gzip: Optional[str] = None,
-        collapses: List[str] = [],
+        collapses: Optional[List[str]] = None,
         limit: Optional[str] = None,
         max_tries: int = 3,
     ) -> None:
         self.url = str(url).strip().replace(" ", "%20")
         self.user_agent = user_agent
-        self.start_timestamp = (
-            str(start_timestamp) if start_timestamp is not None else None
-        )
-        self.end_timestamp = str(end_timestamp) if end_timestamp is not None else None
-        self.filters = filters
+        self.start_timestamp = None if start_timestamp is None else str(start_timestamp)
+        self.end_timestamp = None if end_timestamp is None else str(end_timestamp)
+        self.filters = [] if filters is None else filters
         check_filters(self.filters)
-        self.match_type = str(match_type).strip() if match_type is not None else None
+        self.match_type = None if match_type is None else str(match_type).strip()
         check_match_type(self.match_type, self.url)
         self.gzip = gzip
-        self.collapses = collapses
+        self.collapses = [] if collapses is None else collapses
         check_collapses(self.collapses)
-        self.limit = limit if limit is not None else 5000
+        self.limit = 5000 if limit is None else limit
         self.max_tries = max_tries
         self.last_api_request_url: Optional[str] = None
         self.use_page = False
diff --git a/waybackpy/cli.py b/waybackpy/cli.py
index adf41d0..d1d9aa4 100644
--- a/waybackpy/cli.py
+++ b/waybackpy/cli.py
@@ -16,7 +16,6 @@ from .utils import DEFAULT_USER_AGENT
 from .wrapper import Url
 
 
-@click.command()
 @click.option(
     "-u", "--url", help="URL on which Wayback machine operations are to be performed."
 )
@@ -29,7 +28,13 @@ from .wrapper import Url
 )
 @click.option("-v", "--version", is_flag=True, default=False, help="waybackpy version.")
 @click.option(
-    "-l", "--license", is_flag=True, default=False, help="license of Waybackpy."
+    "-l",
+    "--license",
+    "--show-license",
+    "--show_license",
+    is_flag=True,
+    default=False,
+    help="license of Waybackpy.",
 )
 @click.option(
     "-n",
@@ -125,6 +130,8 @@ from .wrapper import Url
 @click.option(
     "-f",
     "--filter",
+    "--cdx-filter",
+    "--cdx_filter",
     multiple=True,
     help="Filter on a specific field or all the CDX fields.",
 )
@@ -163,11 +170,11 @@ from .wrapper import Url
     + "if this parameter is not used then the plain text response of the CDX API "
     + "will be printed.",
 )
-def main(
+def _main(
     url: Optional[str],
     user_agent: str,
     version: bool,
-    license: bool,
+    show_license: bool,
     newest: bool,
     oldest: bool,
     json: bool,
@@ -185,7 +192,7 @@ def main(
     cdx: bool,
     start_timestamp: Optional[str],
     end_timestamp: Optional[str],
-    filter: List[str],
+    cdx_filter: List[str],
     match_type: Optional[str],
     gzip: Optional[str],
     collapse: List[str],
@@ -218,7 +225,7 @@ def main(
         click.echo(f"waybackpy version {__version__}")
         return
 
-    if license:
+    if show_license:
         click.echo(
             requests.get(
                 url="https://raw.githubusercontent.com/akamhy/waybackpy/master/LICENSE"
@@ -344,7 +351,7 @@ def main(
                 click.echo(url)
 
     if cdx:
-        filters = list(filter)
+        filters = list(cdx_filter)
         collapses = list(collapse)
         cdx_print = list(cdx_print)
 
@@ -397,5 +404,9 @@ def main(
                 click.echo(output_string)
 
 
+def main() -> None:
+    click.command()(_main)
+
+
 if __name__ == "__main__":
     main()
diff --git a/waybackpy/wrapper.py b/waybackpy/wrapper.py
index 38dd1b6..f1154fe 100644
--- a/waybackpy/wrapper.py
+++ b/waybackpy/wrapper.py
@@ -6,21 +6,21 @@ from .cdx_api import WaybackMachineCDXServerAPI
 from .save_api import WaybackMachineSaveAPI
 from .utils import DEFAULT_USER_AGENT
 
-"""
-The Url class is not recommended to be used anymore, instead use the
-WaybackMachineSaveAPI, WaybackMachineAvailabilityAPI and WaybackMachineCDXServerAPI.
-
-The reason it is still in the code is backwards compatibility with 2.x.x versions.
-
-If were are using the Url before the update to version 3.x.x, your code should still be
-working fine and there is no hurry to update the interface but is recommended that you
-do not use the Url class for new code as it would be removed after 2025 also the first
-3.x.x versions was released in January 2022 and three years are more than enough to
-update the older interface code.
-"""
-
 
 class Url(object):
+    """
+    The Url class is not recommended to be used anymore, instead use the
+    WaybackMachineSaveAPI, WaybackMachineAvailabilityAPI and WaybackMachineCDXServerAPI.
+
+    The reason it is still in the code is backwards compatibility with 2.x.x versions.
+
+    If were are using the Url before the update to version 3.x.x, your code should still be
+    working fine and there is no hurry to update the interface but is recommended that you
+    do not use the Url class for new code as it would be removed after 2025 also the first
+    3.x.x versions was released in January 2022 and three years are more than enough to
+    update the older interface code.
+    """
+
     def __init__(self, url: str, user_agent: str = DEFAULT_USER_AGENT) -> None:
         self.url = url
         self.user_agent = str(user_agent)