Customising form rows in a collection form field - php

Question

I am trying to customise a specific form row in my form layout. From the symfony cookbook it tells me, if i understand correctly, that I can modify the form by adding a code block in my form theme file.
I am adding the field to the form like this:
->add('editions', 'collection',
array('type' => new EditionType(),
'allow_add' => true,
'allow_delete' => true,
'by_reference' => false,
)
)
I generate the form rows in the template in the following way, I need the data-prototype tag because the user needs to possibility to add an edition when viewing the form:
<div class="editions" data-prototype="{{ form_widget(form.editions.vars.prototype)|e }}">
{% for edition in form.editions %}
<section class="edition-container">
{{ form_label(edition.isbn) }}
{{ form_errors(edition.isbn) }}
{{ form_widget(edition.isbn) }}
</section>
{% endfor %}
</div>
To customise the rows for the 'editions' fields I tried the following:
<!-- Custom form theme for textarea label rows -->
{% block textarea_label %}
{% spaceless %}
<div {{ block('label_container_attributes') }}>
<label class="label">{{ label }}</label>
</div>
{% endspaceless %}
{% endblock %}
<!-- Custom form theme for edition field textarea label rows -->
{% block _booklist_editions_label %}
{% spaceless %}
<div {{ block('label_container_attributes') }}>
<label class="label">{{ label }}!</label>
</div>
{% endspaceless %}
{% endblock %}
Unfortunately the second block isn't working, the first block however does work. What I did notice is that the outer div from the editions field does not have an id attribute with the field name in it.
This makes me think that the solution to the problem could be one of these:
Custom form theme block has the wrong name, don't know what other name I should give it then.
The id's is not added to the outer div, therefor it's not 'linking' the custom form style.
Could someone explain me how I can add a custom form theme to my 'editions' field using an external form theme file or how I can achieve this in another way.