What is the method for verifying if a field in Drupal 8 is vacant?

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In Drupal 8, you can use the function empty() to check if a field is vacant or not.

Here's an example code snippet:

if (empty($node->field_name->value)) {
  // The field is vacant
} else {
  // The field has content
}

In the above example, replace field_name with the machine name of the field you want to check.

Note: If the field uses a different type of data structure (e.g. for multi-value fields), you may need to adjust the syntax accordingly.