code: def find_user(self, username=None, email=None):
          
          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()
              )
docs: Finds user by username or email