`C14N 2.0<https://www.w3.org/TR/xml-c14n2/>`_ transformation function.

Canonicalization is a way to normalise XML output in a way that allows

byte-by-byte comparisons and digital signatures. Itreduced the freedom

byte-by-byte comparisons and digital signatures. Itreduces the freedom

that XML serializers have and instead generates a more constrained XML

representation. The main restrictions regard the placement of namespace

declarations, the ordering of attributes, and ignorable whitespace.