change return users

        except Exception as e:

            return "Error when retreiving event: ", e

    def get_user(self, id=None):

        user_col = self.db.get_col_by_name_register(self.db.user)

    def get_user(self):

        try:

            list_user = []

            if id == None:

                user = user_col.find({}, {"_id": 0})

            else:

                user = user_col.find({"$or": [

                    { "list_invokers": { "$elemMatch": { "$eq": id } } },

                    { "list_providers": { "$elemMatch": { "$eq": id } } }

                ]}, 

                {"_id": 0})

                list_user.append(user)

            json_users = self.retrieve_users()

            return jsonify(json_users), 200

        except Exception as e:

            return "Error when retrieving users list: ", e

            return jsonify(message="lista de usuarios",

                           object=list_user), 200

        except Exception as e:

            return "Error when retreiving event: ", e

    def retrieve_users(self):

        user_col = self.db.get_col_by_name_register(self.db.user)

        users = user_col.find({}, {"_id": 0})

        json_users = []

        for user in users:

            json_users.append(user)

        return json_users

    def get_num_user(self, id=None):

        user_col = self.db.get_col_by_name_register(self.db.user)