[processing] Make model to/from variant methods public

python/core/auto_generated/processing/models/qgsprocessingmodelalgorithm.sip.in

@@ -291,6 +291,26 @@ Writes the model to a file, at the specified ``path``.
 Reads the model from a file, at the specified ``path``.
 
 .. seealso:: :py:func:`toFile`
+%End
+
+    QVariant toVariant() const;
+%Docstring
+Saves this model to a QVariantMap, wrapped in a QVariant.
+You can use QgsXmlUtils.writeVariant to save it to an XML document.
+
+.. seealso:: :py:func:`loadVariant`
+
+.. versionadded:: 3.4
+%End
+
+    bool loadVariant( const QVariant &variant );
+%Docstring
+Loads this model from a QVariantMap, wrapped in a QVariant ``variant``.
+You can use QgsXmlUtils.readVariant to load it from an XML document.
+
+.. seealso:: :py:func:`toVariant`
+
+.. versionadded:: 3.4
 %End
 
     QVariantMap &helpContent();

src/core/processing/models/qgsprocessingmodelalgorithm.h

@@ -251,6 +251,24 @@ class CORE_EXPORT QgsProcessingModelAlgorithm : public QgsProcessingAlgorithm
      */
     bool fromFile( const QString &path );
 
+    /**
+     * Saves this model to a QVariantMap, wrapped in a QVariant.
+     * You can use QgsXmlUtils::writeVariant to save it to an XML document.
+     *
+     * \see loadVariant()
+     * \since QGIS 3.4
+     */
+    QVariant toVariant() const;
+
+    /**
+     * Loads this model from a QVariantMap, wrapped in a QVariant \a variant.
+     * You can use QgsXmlUtils::readVariant to load it from an XML document.
+     *
+     * \see toVariant()
+     * \since QGIS 3.4
+     */
+    bool loadVariant( const QVariant &variant );
+
     /**
      * Returns the model's help contents (a free-form map of values describing the algorithm's
      * use and metadata).
@@ -387,22 +405,6 @@ class CORE_EXPORT QgsProcessingModelAlgorithm : public QgsProcessingAlgorithm
      */
     bool childOutputIsRequired( const QString &childId, const QString &outputName ) const;
 
-    /**
-     * Saves this model to a QVariantMap, wrapped in a QVariant.
-     * You can use QgsXmlUtils::writeVariant to save it to an XML document.
-     *
-     * \see loadVariant()
-     */
-    QVariant toVariant() const;
-
-    /**
-     * Loads this model from a QVariantMap, wrapped in a QVariant.
-     * You can use QgsXmlUtils::readVariant to load it from an XML document.
-     *
-     * \see toVariant()
-     */
-    bool loadVariant( const QVariant &model );
-
     /**
      * Checks whether the output vector type given by \a outputType is compatible
      * with the list of acceptable data types specified by \a acceptableDataTypes.