code: def add_marccountry_tag(dom):
      
      marccountry = dom.find("mods:placeTerm", {"authority": "marccountry"})
  
      # don't add again if already defined
      if marccountry:
          return
  
      marccountry_tag = dhtmlparser.HTMLElement(
          "mods:place",
          [
              dhtmlparser.HTMLElement(
                  "mods:placeTerm",
                  {"type": "code", "authority": "marccountry"},
                  [dhtmlparser.HTMLElement("xr-")]
              )
          ]
      )
      insert_tag(
          marccountry_tag,
          dom.match("mods:mods", "mods:originInfo", "mods:place"),
          first(dom.find("mods:originInfo"))
      )
docs: Add ``<mods:placeTerm>`` tag with proper content.