def emit_element( output_node, element_name, attr_hash=nil )
      if (attr_hash != nil) then
        attr_hash.each do |key, value|
          if (value == nil) then
            attr_hash.delete( key )
          end
        end
        if attr_hash.empty? then
          attr_hash = nil
        end
      end
      output_node.add_element( element_name, attr_hash )
    end
def emit_element( output_node, element_name, attr_hash=nil )
      if (attr_hash != nil) then
        attr_hash.each do |key, value|
          if (value == nil) then
            attr_hash.delete( key )
          end
        end
        if attr_hash.empty? then
          attr_hash = nil
        end
      end
      output_node.add_element( element_name, attr_hash )
    end
Emit an element with the given <tt>element_name</tt> and
 <tt>attr_hash</tt> (as attributes) as a child of the
 <tt>output_node</tt>