def footer=(footer)
         if footer.type == FooterNode::UNIVERSAL
            @footers[0] = footer
         elsif footer.type == FooterNode::LEFT_PAGE
            @footers[1] = footer
         elsif footer.type == FooterNode::RIGHT_PAGE
            @footers[2] = footer
         elsif footer.type == FooterNode::FIRST_PAGE
            @footers[3] = footer
         end
      end
def footer=(footer)
         if footer.type == FooterNode::UNIVERSAL
            @footers[0] = footer
         elsif footer.type == FooterNode::LEFT_PAGE
            @footers[1] = footer
         elsif footer.type == FooterNode::RIGHT_PAGE
            @footers[2] = footer
         elsif footer.type == FooterNode::FIRST_PAGE
            @footers[3] = footer
         end
      end
This method assigns a new footer to a document. A Document object can
 have up to four footers - a default footer, a footer for left pages, a
 footer for right pages and a footer for the first page. The method
 checks the footer type and stores it appropriately.

 ==== Parameters
 footer::  A reference to the footer object to be stored. Existing footer
           objects are overwritten.