[BUG][typescript-rxjs] Unnecessary imports occurs when using allOf

[tanmen]

Bug Report Checklist

• Have you provided a full/minimal spec to reproduce the issue?
• Have you validated the input using an OpenAPI validator (example)?
• What's the version of OpenAPI Generator used?
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• What's the actual output vs expected output?
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Description

If allOf is used, a model that does not use import will be generated.
Because my project prohibits unused import, an error occurs in typescript.
import must be used or deleted.

taget schemas

    Response:
      type: string
      example: success
      enum:
        - success
        - error
    Box:
      type: object
      properties:
        id:
          type: number
          example: 1
        name:
          type: string
          example: inbox
    BoxesResponse:
      allOf:
        - $ref: '#/components/schemas/Response'
        - $ref: '#/components/schemas/Box'

generated typescript file

// tslint:disable
/**
 * My application
 * My application
 *
 * The version of the OpenAPI document: 1.0.0
 * 
 *
 * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
 * https://openapi-generator.tech
 * Do not edit the class manually.
 */

 import {
     Box,
     Response,
 } from './';

 /**
  * @export
  * @interface BoxResponse
  */
 export interface BoxResponse extends Box, Response{
     /**
      * @type {string}
      * @memberof BoxResponse
      */
     status?: BoxResponseStatusEnum;
     /**
      * @type {number}
      * @memberof BoxResponse
      */
     id?: number;
     /**
      * @type {string}
      * @memberof BoxResponse
      */
     name?: string;
 }

 /**
  * @export
  * @enum {string}
  */
 export enum BoxResponseStatusEnum {
     Success = 'success',
     Error = 'error'
 }

expected

// tslint:disable
/**
 * My application
 * My application
 *
 * The version of the OpenAPI document: 1.0.0
 * 
 *
 * NOTE: This class is auto generated by OpenAPI Generator (https://openapi-generator.tech).
 * https://openapi-generator.tech
 * Do not edit the class manually.
 */

import {
    Box,
    Response,
} from './';

/**
 * @export
 * @interface BoxResponse
 */
export interface BoxResponse extends Box, Response {
}

openapi-generator version

4.2.0

OpenAPI declaration file content or url

openapi: 3.0.2
info:
  title: My application
  version: 1.0.0
  description: My application
tags:
  - name: Box
paths:
  /boxes:
    get:
      summary: Box list
      description: Box list
      operationId: showBoxes
      tags:
        - Box
      responses:
        200:
          description: Box list
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/BoxesResponse'
components:
  schemas:
    Response:
      type: string
      example: success
      enum:
        - success
        - error
    Box:
      type: object
      properties:
        id:
          type: number
          example: 1
        name:
          type: string
          example: inbox
    BoxesResponse:
      allOf:
        - $ref: '#/components/schemas/Response'
        - $ref: '#/components/schemas/Box'

Command line used for generation

$ openapi-generator generate -i openapi.yml -g typescript-rxjs -o apis

Steps to reproduce

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Related issues/PRs

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Suggest a fix

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