Changes

vendor/phpoffice/math/src/Math/Writer/MathML.php

@@ -40,6 +40,26 @@ class MathML implements WriterInterface
     {
         $tagName = $this->getElementTagName($element);
 
+        // Element\AbstractGroupElement
+        if ($element instanceof Element\Semantics) {
+            $this->output->startElement($tagName);
+            // Write elements
+            foreach ($element->getElements() as $childElement) {
+                $this->writeElementItem($childElement);
+            }
+
+            // Write annotations
+            foreach ($element->getAnnotations() as $encoding => $annotation) {
+                $this->output->startElement('annotation');
+                $this->output->writeAttribute('encoding', $encoding);
+                $this->output->text($annotation);
+                $this->output->endElement();
+            }
+            $this->output->endElement();
+
+            return;
+        }
+
         // Element\AbstractGroupElement
         if ($element instanceof Element\AbstractGroupElement) {
             $this->output->startElement($tagName);
@@ -121,6 +141,9 @@ class MathML implements WriterInterface
         if ($element instanceof Element\Operator) {
             return 'mo';
         }
+        if ($element instanceof Element\Semantics) {
+            return 'semantics';
+        }
 
         throw new NotImplementedException(sprintf(
             '%s : The element of the class `%s` has no tag name',