docs: def add_credential(self, url, username, password):
          """
          Check if this credential has already been added to the database, if not add it in.
          """
          cur = self.conn.cursor()
  
          cur.execute("SELECT * FROM credentials WHERE LOWER(username)=LOWER(?) AND password=?", [url, username, password])
          results = cur.fetchall()
  
          if not len(results):
              cur.execute("INSERT INTO credentials (username, password) VALUES (?,?)", [username, password] )
  
          cur.close()