Can't locate object method in my Moo based class

[Lotus1]

This is my first non-trivial attempt at Perl object oriented programming. The code below is just a first attempt to get something simple working but I'm stumped.

Goal: Add my own methods in my XML::LibXML derived objects.

Problem: The method I added in SSEDocument can't be located when I run my test script. I want my method to be similar to findnodes. findnodes and findvalue are defined in XML::LibXML::Node. The documentation for XML::LibXML::Document states that it inherits all the methods from XML::LibXML::Node. If I make my own version of XML::LibXML::Node then the methods there won't be seen since XML::LibXML::Document will still inherit from XML::LibXML::Node. I don't understand why my method won't work when defined in SSEDocument. Can someone suggest a better approach?

package SSEParser;
use Moo;
use Data::Dumper;
extends 'XML::LibXML';

sub load_sse_file {
    my ($self, $filename) = @_;
    die "File not found <$filename>\n" unless -f $filename;
    die "Not SSE file <$filename>\n" unless $filename =~ /_subeditor\.
+xml$/i;
    my $doc  = $self->parse_file($filename);
    print '='x75, "\n";
    print Dumper($doc);
    print '='x75, "\n";
    bless $doc, 'SSEDocument';
    return $doc;
}
1;

package SSEDocument;
use Moo;
extends 'XML::LibXML::Document';

sub find_buses {
    my ($self) = @_;
    return $self->findnodes("//DNOM/Substation/Bus");
}
1;

testmyclass.pl

#!/usr/bin/perl
use warnings;
use strict;
use Data::Dumper;
use SSEParser;

my $inst = SSEParser->new();
print Dumper($inst);
my $sse_doc = $inst->load_sse_file("test_subeditor.xml");
print Dumper($sse_doc);

my @buses = $sse_doc->find_buses();

When I run this here are the results:

$VAR1 = bless( {
                 '_State_' => 0,
                 'XML_LIBXML_PARSER_OPTIONS' => 4102
               }, 'SSEParser' );
======================================================================
+=====
$VAR1 = bless( do{\(my $o = 68387856)}, 'XML::LibXML::Document' );
======================================================================
+=====
$VAR1 = bless( do{\(my $o = 68387856)}, 'SSEDocument' );
Can't locate object method "find_buses" via package "SSEDocument" at C
+:\usr\scripts\SSE\sseparser\pm\testmyclass.pl line 12.

[Anonymous Monk]

Did you forget  use SSEDocument ; ?

[Lotus1]

Doh! I didn't exactly forget it, I assumed I didn't need it since when I use XML::LibXML I don't have to worry about 'use'ing all the sub classes. But XML::LibXML must be taking care of all the importing and namespace stuff in the background. Thanks, it works now.