check for duplicate themes

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
@author: rohezal
"""

def cleanTheme(theme):
    filler_words = ["the", "and", "an", "a", "or", "is", "was", ".", "...", "!", "?", ","]
    theme = theme.lower()
    theme_as_list = theme.split(" ")
    clean_theme = ""
    for word in theme_as_list:
        if word not in filler_words:
            clean_theme = clean_theme  + word + " "
    clean_theme = clean_theme.strip()
    return clean_theme

def findSimilarThemes(new_theme, themes):
    new_theme_list = new_theme.split()
    result_list = []
    for existing_theme in themes:
        existing_theme_list = existing_theme.split()
        for word in new_theme_list:
            if word in existing_theme_list:
                result_list.append(existing_theme)
                break
    return result_list

def checkForDuplicateTheme(new_theme, themes):
    return new_theme in themes


suggested_themes = ["Loving the whole world", "The dog is evil", "Enough is enough", "And the world is not enough ..."]
suggested_themes_clean = []

for theme in suggested_themes:
    suggested_themes_clean.append(cleanTheme(theme))

mytheme = "The world is not enough"
clean_theme = cleanTheme(mytheme)
matching_themes = findSimilarThemes(clean_theme,suggested_themes_clean)
is_duplicate = checkForDuplicateTheme(clean_theme, suggested_themes_clean)

print (clean_theme)
print(matching_themes)
print("Is duplicated: " + str(is_duplicate))