How to use the ngx-validators.UniversalValidators.isNumber function in ngx-validators

UniversalValidators.noEmptyString
  ]));

  min: FormControl = new FormControl('', Validators.compose([
    Validators.required,
    UniversalValidators.min(5)
  ]));

  max: FormControl = new FormControl('', Validators.compose([
    Validators.required,
    UniversalValidators.max(10)
  ]));

  isNumber: FormControl = new FormControl('', Validators.compose([
    Validators.required,
    UniversalValidators.isNumber
  ]));

  isInRange: FormControl = new FormControl('', Validators.compose([
    Validators.required,
    UniversalValidators.isInRange(3, 6)
  ]));

  maxLength: FormControl = new FormControl('', Validators.compose([
    Validators.required,
    UniversalValidators.maxLength(5)
  ]));

  minLength: FormControl = new FormControl('', Validators.compose([
    Validators.required,
    UniversalValidators.minLength(3)
  ]));