Mimicing is an argument, not object.

The mimicking() function now uses the passed material instance
instead of saving the material instance as part of the other
material instance (confusing, huh?).

The material can be instantiated by:

material = Material("elastic", parameters=parameters, switch=["foo:bar"])

Switch options passed in this way take precedence over the rcfile options,
however passed options do not clobber rcfile options. So, if you pass
"foo:bar" and have "foo:baz" in your rcfile, it will run with "bar" not
"baz".