How to change the markup for a field

I’d like to change the output from the field formatter view from the Field API. I’d like a cleaner markup without unnecessary tags. What’s the best way to clean up field formatter view output? Many thanks.

Ideally to change from this:

<div class="field field--name-field-visualisation field--type-mango-maker field--label-above">     <div class="field__label">Visualisation:&nbsp;</div>     <div class="field__items">         <div class="field__item even">             <div class="something"></div>         </div>     </div> </div> 

to this:

<div class="field field--name-field-visualisation field--type-mango-maker field--label-above">     <div class="field__label">Visualisation:&nbsp;</div>     <div class="something"></div> </div> 

heres my hook_function_field_formatter_view function:

function mango_field_formatter_view($  entity_type, $  entity, $  field, $  instance, $  langcode, $  items, $  display) {    $  output[0] = array(     '#theme' => 'container',     '#attributes' => array(       'class' => array('something'),     ),   );   return $  output; }