diff --git a/jdog/cli.py b/jdog/cli.py
index f2bb7a1..cacbcdb 100644
--- a/jdog/cli.py
+++ b/jdog/cli.py
@@ -5,7 +5,7 @@
 from faker.config import AVAILABLE_LOCALES
 
 
-def callback_lang_help(ctx, prop, value):
+def _lang_help(ctx, prop, value):
     if not value:
         return
     click.echo('Use one of the following language code: ')
@@ -13,14 +13,14 @@ def callback_lang_help(ctx, prop, value):
     ctx.exit()
 
 
-def validate_lang(ctx, prop, value):
+def _validate_lang(ctx, prop, value):
     if value not in AVAILABLE_LOCALES:
         raise click.BadParameter('Language code is invalid. See --lang-help for accepted values')
 
     return value
 
 
-def print_output(result, pretty, output):
+def _print_output(result, pretty, output):
     if pretty:
         pretty_output = json.dumps(json.loads(result), indent=4)
         if output:
@@ -43,17 +43,18 @@ def print_output(result, pretty, output):
 @click.argument('scheme', type=click.File('r'))
 @click.option('-p', '--pretty', is_flag=True, default=False, help='Output as pretty JSON.')
 @click.option('-s', '--strict', is_flag=True, default=False, help='Raise error when no matching placeholder is found.')
-@click.option('-l', '--lang', default='en_US', help='Language to use', callback=validate_lang)
-@click.option('--lang-help', is_flag=True, default=False, help='Displays available language codes and exit.', callback=callback_lang_help)
+@click.option('-l', '--lang', default='en_US', help='Language to use.', callback=_validate_lang)
+@click.option('--lang-help', is_flag=True, default=False, help='Displays available language codes and exit.',
+              callback=_lang_help)
 @click.option('-o', '--output', type=click.File('w'), help='Output file where result is written.')
-def run(scheme,strict, pretty, lang, lang_help, output):
+def run(scheme, strict, pretty, lang, lang_help, output):
     """Accepts SCHEME and generate new data to stdin or to specified OUTPUT"""
     try:
         jdog = Jdog(lang, strict)
         scheme_text = scheme.read()
         jdog.parse_scheme(scheme_text)
         result = jdog.generate()
-        print_output(result, pretty, output)
+        _print_output(result, pretty, output)
     except json.JSONDecodeError as e:
         raise click.UsageError(f'Provided SCHEME does not have valid JSON format.\n\tJsonError: {e}')
     except NoMatchingPlaceholder as e: