Returns list of field names for the given paragraph type and field type.
\Drupal\paragraphs\Entity\ParagraphsType $paragraphs_type: The paragraphs type entity.
string $field_type: (optional) Field type to check for existence. If field type is not provided, returns all entity fields.
string[] The list of field labels keyed by their field name.
public function getFieldNameOptions(ParagraphsType $paragraphs_type, $field_type = NULL);