class Builder::XmlBase

cf. http://fishbowl.pastiche.org/2004/10/13/cargo_cult_programming).
cargo cult programming,
is pretty safe to define it here. (Note: this is an example of
of recursion happens. Since nil? won't ever be an XML tag, it
is not defined and method_missing is invoked, some strange kind
For some reason, nil? is sent to the XmlMarkup object. If nil?

def nil?
  false
end