Function _assignValidators

packages/forms/src/model/abstract_model.ts:1790–1794

* Internal implementation of the `setValidators` method. Needs to be separated out into a * different method, because it is called in the constructor and it can break cases where * a control is extended.

(validators: ValidatorFn | ValidatorFn[] | null)

   * a control is extended.
   */
  private _assignValidators(validators: ValidatorFn | ValidatorFn[] | null): void {
    this._rawValidators = Array.isArray(validators) ? validators.slice() : validators;
    this._composedValidatorFn = coerceToValidator(this._rawValidators);
    this._updateHasRequiredValidator();
  }

  /**
   * Internal implementation of the `setAsyncValidators` method. Needs to be separated out into a