Typically HTTP headers work like a `Map<String, String>`: each field has one value or none. But some headers permit multiple values, like Guava's [Multimap](https://guava.dev/releases/23.0/api/docs/com/google/common/collect/Multimap.html). For example, it's legal and common for an HTTP response to supply multiple `Vary` headers. OkHttp's APIs attempt to make both cases comfortable.

// dish : 2015-07-30 Dish DBS Corporation
dish

// diy : 2015-11-05 Lifestyle Domain Holdings, Inc.
diy

// dnp : 2013-12-13 Dai Nippon Printing Co., Ltd.
dnp

// docs : 2014-10-16 Charleston Road Registry Inc.
docs

// doctor : 2016-06-02 Binky Moon, LLC
doctor

// dog : 2014-12-04 Binky Moon, LLC
dog

// domains : 2013-10-17 Binky Moon, LLC
domains

FDC1          ; mapped                 ; 0641 0645 064A #1.1  ARABIC LIGATURE FEH WITH MEEM WITH YEH FINAL FORM
FDC2          ; mapped                 ; 0628 062D 064A #1.1  ARABIC LIGATURE BEH WITH HAH WITH YEH FINAL FORM
FDC3          ; mapped                 ; 0643 0645 0645 #1.1  ARABIC LIGATURE KAF WITH MEEM WITH MEEM INITIAL FORM
FDC4          ; mapped                 ; 0639 062C 0645 #1.1  ARABIC LIGATURE AIN WITH JEEM WITH MEEM INITIAL FORM