Finds user by username or email

def find_user(self, username=None, email=None):
        """
            Finds user by username or email
        """
        if username:
            return (
                self.get_session.query(self.user_model)
                .filter(func.lower(self.user_model.username) == func.lower(username))
                .first()
            )
        elif email:
            return (
                self.get_session.query(self.user_model).filter_by(email=email).first()
            )