I'm trying to use report parser, but it always pop an error 

ValueError  The _name attribute report.test_module.report_test_doc is not valid

I searched that your report name is use for the parser _template and _name in order to be used by Odoo. It doesn't show the error if I remove the test_module, but the hello() is not callable.

report.xml

<?xml version="1.0" encoding="utf-8"?>
<openerp>
    <data>
    	<report 
            id="eport_monthly_pdc"
            string="Monthly report of PDC"
            model="account.voucher"
            report_type="qweb-pdf"
            name="test_module.report_test_doc" 
            file="test_module.report_test_doc" 
        />
    </data>
</openerp>

report_parser.py

from openerp import api, models
from openerp.report import report_sxw
import time
class report_parser(report_sxw.rml_parse):
    def __init__(self, cr, uid, name, context):
        super(report_parser, self).__init__(cr, uid, name, context=context)
        self.localcontext.update({     
            'time': time,            
            'hello_world': self._hello,
        })
    def _hello(self):
        return "Hello World!"

class report_parser_test(models.AbstractModel):
    _name = 'report.test_module.report_test_doc'
    _inherit = 'report.abstract_report'
    _template = 'test_module.report_test_doc'
    _wrapped_report_class = pdc_report_parser