default_get records from data file

Question

how can i pre load records from data by default_get method.

i have data file with this kind of records data/project_data.xml

<record id="project_document_type_gal" model="project.part.template">
        <field name="code">ŪK</field>
        <field name="sequence">49</field>
        <field name="group_id" ref="project_custom.project_document_kv"/>
        <field name="description">UK (UK)</field>
    </record>

    <record id="project_document_type_sem" model="project.part.template">
        <field name="code">SEM</field>
        <field name="sequence">50</field>
        <field name="group_id" ref="project_custom.project_document_kv"/>
        <field name="description">SEM (SEM)</field>
    </record>

class ProjectPartTemplate(models.Model):
    _name = 'project.part.template'
    _inherit = 'project.object'


class ProjectObject(models.AbstractModel):
    _name = 'project.object'
    _rec_name = 'code'

    sequence = fields.Integer('Sequence')
    code = fields.Char('Code', required=True)
    description = fields.Char(required=True)
    project_default_stage = fields.Boolean(
        'Default for new projects',
        help='Will be used for new projects', default=True)

and wizard.

class ProjectPartWizard(models.TransientModel):
    _name = 'project.part.wizard'
    _description = 'Part wizard'

    part_ids = fields.Many2many('project.part')

    @api.model
    def default_get(self, fields_list):
        result = super(ProjectPartWizard, self).default_get(fields_list)
        part_ids = []
        if self._context.get('active_model') == 'project.project':
            project = self.env['project.project'].browse(
                self._context.get('active_id'))
            project and part_ids.extend(project.project_part_ids.ids)
        # TODO load all part from template
        result.update(part_ids=[(6, 0, part_ids)])

        return result

UPDATE

<xpath expr="//field[@name='task_count']/.." position="before">
                    <button string="Generate Parts" class="oe_stat_button"
                            name="%(project_part_wizard_action)d"
                            type="action" icon="fa-th">
                    </button>
                </xpath>

here is button

so there is a templates and i need to that all templates would be in wizard pre-loaded when i open it. how can i do it with default_get