How to have marshmallow definitions and multi-version specs together in flasgger?

Finally, I found a solution (maybe not the best, but it works fine).

It's easy, just remove the template argument from Swagger(...) input, instead of that, add definitions to configs dict. Let's see the final result:

from app.api.v1.controllers.assessment_controller import AssessmentCoachingRequestSchema, AssessmentCoachingResponseSchemafrom app.api.v1.responses import AssessmentResultResponseSchema, ModuleScoreResponseSchema, RecommendedModulesListResponseSchema, UserModuleScoresListResponseSchemafrom app.api.v1.requests import AssessmentCreateRequestSchema, AssessmentShowRequestSchemafrom app.api.v1.routes import assesmentfrom flasgger import Swaggerfrom flask.app import Flaskfrom flasgger import APISpec, Schema, Swagger, fieldsfrom apispec.ext.marshmallow import MarshmallowPluginfrom apispec_webframeworks.flask import FlaskPlugindef configure_swagger(app: Flask):    # Create an APISpec    spec = APISpec(        title='API',        version='1.0.0',        openapi_version='2.0',        plugins=[            FlaskPlugin(),            MarshmallowPlugin(),        ],    )    template = spec.to_flasgger(        app,        definitions=[AssessmentCreateRequestSchema, AssessmentResultResponseSchema,                     AssessmentShowRequestSchema, AssessmentCoachingRequestSchema,                     AssessmentCoachingResponseSchema, UserModuleScoresListResponseSchema,                     RecommendedModulesListResponseSchema]    )    configs = {        "headers": [        ],        "definitions":template['definitions'],        "specs": [            {                "endpoint": 'v0_spec',                "route": '/v0',                "version": "0.0.0",                "title": "API v0",                "description": 'Version 0 of the API',                "rule_filter": lambda rule: rule.endpoint.startswith('api_v0'),                "model_filter": lambda tag: True,  # all in            },            {                "endpoint": 'v1_spec',                "route": '/v1',                "version": "1.0.0",                "title": "API v1",                "description": 'Version 1 of the API',                "rule_filter": lambda rule: rule.endpoint.startswith('api_v1'),                "model_filter": lambda tag: True,  # all in            },            {                "endpoint": 'test_v1_spec',                "route": '/tv1',                "version": "1.0.0",                "title": "API test v1",                "description": 'Test version 1 of the API',                "rule_filter": lambda rule: rule.endpoint.startswith('api_test_v1'),                "model_filter": lambda tag: True,  # all in            },            {                "endpoint": 'experiment_v1_spec',                "route": '/exp',                "version": "1.0.0",                "title": "API experiment",                "description": 'Experiment API',                "rule_filter": lambda rule: rule.endpoint.startswith('api_exp'),                "model_filter": lambda tag: True,  # all in            }        ],        "static_url_path": "/flasgger_static",        # "static_folder": "static",  # must be set by user        "swagger_ui": True,        "specs_route": "/apidocs/",        "title": "API",        "schemes": [            "http",            "https"        ],        "securityDefinitions": {            "basicAuth": {                "type": "http",                "scheme": "basic"            }        },        "security":{"basicAuth": []}    }    swag = Swagger(app, config=configs)