def numerate(a=[])
			self.section_number = a
			section_children.each_with_index do |c,i|
				c.numerate(a.clone.push(i+1))
			end
			if h = self.header_element
				h.attributes[:section_number] = self.section_number
			end
		end
def numerate(a=[])
			self.section_number = a
			section_children.each_with_index do |c,i|
				c.numerate(a.clone.push(i+1))
			end
			if h = self.header_element
				h.attributes[:section_number] = self.section_number
			end
		end
Numerate this section and its children