public function addCustomer(Customer $l)
    {
        if ($this->collCustomers === null) {
            $this->initCustomers();
            $this->collCustomersPartial = true;
        }

        if (!in_array($l, $this->collCustomers->getArrayCopy(), true)) { // only add it if the **same** object is not already associated
            $this->doAddCustomer($l);

            if ($this->customersScheduledForDeletion and $this->customersScheduledForDeletion->contains($l)) {
                $this->customersScheduledForDeletion->remove($this->customersScheduledForDeletion->search($l));
            }
        }

        return $this;
    }