I want to change this total label to "Average", How it could be possible ?

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@Axel :

Here is the error : JS test results raising error

And Here is my code :

__openerp__.py

{ 'name''HR appraisals advanced management (Survey enhancements included)': ,
  'description':'Advanced appraisals management' ,
  'author':'Yassine TEIMI ,
  'depends': ['hr_evaluation','survey','web_graph'],

  'data': ['views/survey_templates.xml','views/survey_result.xml','report/hr_evaluation_report_extension_view.xml','static/src/xml/assets_backend.xml'],
}

change_total_label.js : 

(function () {
'use strict';
var _lt = openerp.web._lt;
var _t = openerp.web._t;
openerp.web_graph.PivotTable.include({
    find_or_create_header: function (headers, path, data_pt) {
        var self = this;
        var hdr = _.find(headers, function (header) {
            return self.isEqual(path, header.path);
        });
        if (hdr) {
            return hdr;
        }
        if (!path.length) {
            var pivot_header = 'Total';
            if(self.context.pivot_header != undefined){
                pivot_header = self.context.pivot_header;
            }
            hdr = this.make_header({title: _t(pivot_header)});
            headers.push(hdr);
            return hdr;
        }
        hdr = this.make_header({
            path:path,
            domain:data_pt.model._domain,
            title: _t(_.last(path))
        });
        var parent = _.find(headers, function (header) {
            return self.isEqual(header.path, _.initial(path, 1));
        });
        var previous = parent.children.length ? _.last(parent.children) : parent;
        headers.splice(headers.indexOf(previous) + 1, 0, hdr);
        parent.children.push(hdr);
        return hdr;
    },
});
})();

assets_backend.xml : 

<template id="assets_backend" name="web_graph assets" inherit_id="web.assets_backend">
    <xpath expr="." position="inside">
        <script type="text/javascript" src="/hr_appraisals_adv/static/src/js/change_total_label.js"></script>
    </xpath>
</template>

my reporting action, where I need to passe the pivot header : 

<record id="action_evaluation_goals_reaching" model="ir.actions.act_window">
    <field name="name">Atteinte des objectifs</field>
    <field name="res_model">hr.evaluation.report.goals</field>
    <field name="view_type">form</field>
    <field name="view_mode">graph</field>
    <field name="search_view_id" ref="view_goals_reaching_search"/>
    <field name="context">{'pivot_header': 'Moyenne'}</field> <!-- just added here the label in french -->
</record>