Break LibXML::DocumentFragment parse() method into multis

Make it consistant with LibXML::Parser

Author: dwarring

docs/DocumentFragment.md

@@ -61,10 +61,9 @@ Creates a new empty document fragment to which nodes can be added; typically by
 
 ```raku
 method parse(
-    Str(Any) :$string!,
+    Str:D(Any):D :$string!,
     Bool :balanced($)! where { ... },
-    NativeCall::Types::Pointer :$user-data,
-    |c
+    NativeCall::Types::Pointer :$user-data
 ) returns LibXML::DocumentFragment
 ```
 

lib/LibXML/DocumentFragment.rakumod

@@ -113,16 +113,31 @@ method new(LibXML::Node :doc($_), xmlDocFrag :$native, *%c) {
 =end pod
 
 #| parses a balanced XML chunk
-method parse(
-    Str() :$string!,
+proto method parse(
+    Str:D() :$string!,
+    Bool :balanced($)! where .so,
+    Pointer :$user-data,
+    --> LibXML::DocumentFragment) {
+    {*}
+}
+
+multi method parse(
+  ::?CLASS:U:
+  Str:D() :$string, 
+  Bool :balanced($)! where .so,
+  Pointer :$user-data,
+ |c) is hidden-from-backtrace {
+    self.new(|c).parse: :$string, :balanced, :$user-data, |c;
+}
+
+multi method parse(
+    ::?CLASS:D $doc-frag:
+    Str:D() :$string!,
     Bool :balanced($)! where .so,
     Pointer :$user-data,
     |c
     --> LibXML::DocumentFragment) is hidden-from-backtrace {
 
-    my $doc-frag = self;
-    $_ .= new(|c) without $doc-frag;
-
     my ParserContext $ctx = $doc-frag.create: ParserContext, :$string, :$doc-frag, :$user-data, |c;
 
     $ctx.do: {