Accepted options for Collection: - target_element: an array or element used in the collection - count: number of times the element is added initially - allow_add: if set to true, elements can be added to the form dynamically (using JavaScript) - allow_remove: if set to true, elements can be removed to the form - should_create_template: if set to true, a template is generated (inside a <span>) - template_placeholder: placeholder used in the data template