How to receive 400 error in mock?

[razb-viola]

In success response 200 that have multiple responses examples, I can send this header:
Prefer: example=one
And I will get specific example.

How to get error response with code 400 with example of badUserInput?

Full code example:

      200: {
        description: '',
        content: {
          'application/json': {
            schema: Person
          }
        }
      },
      400: {
        description: 'Bad Request',
        content: {
          'application/json': {
            schema: CustomError,
            examples: {
              badUserInput: {
                value: {
                  name: 'BadRequest',
                  message: 'Invalid user input provided',
                  flags: {
                    firstName: 'Required',
                    lastName: 'At least 2 characters',
                    authenticationMethods: {
                      creds: {
                        username: 'String only'
                      },
                      phone: 'Maximum 25 characters'
                    }
                  }
                }
              },
              invalidPrecondition: {
                value: {
                  name: 'BadRequest',
                  message: 'Maximum 6 Persons can be created',
                }
              }
            }
          }
        }
      },