'Is this tag an empty-element tag? (aka a self-closing tag)
A tag that has contents is never an empty-element tag.
A tag that has no contents may or may not be an empty-element
tag. It depends on the builder used to create the tag. If the
builder has a designated list of empty-element tags, then only
a tag whose name shows up in that list is considered an
empty-element tag.
If the builder has no designated list of empty-element tags,
then any tag with no contents is an empty-element tag.'

@property
def is_empty_element(self):

    return ((len(self.contents) == 0) and self.can_be_empty_element)
