Odoo v10: How to copy the contents of a One2many field into another One2many field?

I would like to know how to copy a One2many field, that is let's say that I have 2 One2many fields that point to different models, and in both models are the same fields, and I want to create a method where all the contents of the first One2many field are copied to me in the second field One2many, I do not know if you explain ... I wait for your answers, Greetings and thanks in advance if you can help me.

Try this test code to see if it worked but I get an error:

def foo(self):
    detalles = self.env['detalle'].browse(self._context.get('active_ids', []))
    obj = self.env['detalle2contract']
    for r in self:
        for d in detalles:
            tipo = d.tipo
            descripcion = d.descripcion
            cantidad = d.cantidad
            unidad = d.unidad
            detalle2contract_id = d.detalle_id

    lines = obj.create({
        'tipo': tipo,
        'descripcion': descripcion,
        'cantidad' cantidad,
        'unidad': unidad,
        'detalle2contract_id': detalle2contract_id
        })

    return lines