Here are some steps that I use for that

1- Copy the text into a simple text editor like Gedit or notepad just to clear the format of the text source

2- Paste it into the place where you wanna have the text at the end

3- Select the text pasted and apply the code style from the wand style dropdown menu

and that's all

Note: Always is better to just left a line at the end of the post with any character just to be able to continue writing after the code style applied

#Edit: Another way that works in more complex scenarios

class purchase_requisition(osv.osv):
    _name = "purchase.requisition"
    _description = "Purchase Requisition"
    _inherit = ['mail.thread', 'ir.needaction_mixin']

    def _get_po_line(self, cr, uid, ids, field_names, arg=None, context=None):
        result = dict((res_id, []) for res_id in ids)
        for element in self.browse(cr, uid, ids, context=context):
            for po in element.purchase_ids:
                result[element.id] += [po_line.id for po_line in po.order_line]
        return result

That's how I do it

This is the screencast: