code: def get_first_element_index(root, tag_name):
      
      tag_index = 1
      for tag in root:
          if tag.tag == tag_name:
              # Return the first one found if there is a match
              return tag_index
          tag_index = tag_index + 1
      # Default
      return None
docs: In order to use Element.insert() in a convenient way,
      this function will find the first child tag with tag_name
      and return its index position
      The index can then be used to insert an element before or after the
      found tag using Element.insert()