The copy hash method creates a independent copy of a hash object. Creating
a copy using the assingment operator,
<-, does not work as expected,
since hashes are based on environments and environments are reference objects
in R. The assignment operator consequently creates a linked copy to the
original hash and not an independent copy. The
copy method provides
an identical unlinked copy of the hash.
A hash object.
signature(x = "hash")
Creates and returns an identical, independent, unreferenced copy of the the hash.