Extracts the unit information from the expression, keyed by a
symbolic name for the unit, as defined by the syntax which was
used to parse the expression.
Respond with a Dimensions object which is the result of
multiplying the dimensions of this object by the dimensions of
another raised to the given power.
Produces a string representation of the unit expression, in a
format appropriate to the given syntax, and with output
respecting the conventions of the given locale.