Swift_Mime_CharsetObserver | --Swift_Mime_HeaderSet
Located in File: /vendors/swiftMailer/classes/Swift/Mime/HeaderSet.php
These Headers will be output in the given order where present.
If multiple headers match, the actual one may be specified by $index. Returns NULL if none present.
If multiple headers match, the actual one may be specified by $index.
If multiple headers match, the actual one may be specified by $index.
The header may be a previously fetched header via get() or it may be one that has been created separately.
If $index is specified, the header will be inserted into the set at this offset.
Usually headers without a field value won't be output unless set here.