def update_access(data, *access):
    """Merge access rights information.

    :params data: current JSON structure with metadata and potentially an
        `_access` key.
    :param *access: List of dictionaries to merge to the original data, each of
        them in the form `action: []`.
    """
    current_rules = data.get('_access', {})
    for a in access:
        for k, v in a.items():
            current_x_rules = set(current_rules.get(k, []))
            current_x_rules.update(v)
            current_rules[k] = list(current_x_rules)
    data['_access'] = current_rules
