Zonemaster::LDNS::RR::SPF - Type SPF record
A subclass of Zonemaster::LDNS::RR, so it has all the methods of
    that class available in addition to the ones documented here.
  - spfdata()
- Returns the concatenation of all the strings composing the data of the
      resource record.
    For example, if an SPF resource record has the following
        presentation format:     test.example. 3600 IN SPF "v=spf1 " "mx " "a " "-all"
    then spfdata() returns the string
        "v=spf1 mx a -all".