'Adds to the set of equivalencies enabled in the unit registry.
These equivalencies are used if no explicit equivalencies are given,
both in unit conversion and in finding equivalent units.
This is meant in particular for allowing angles to be dimensionless.
Use with care.
Parameters
equivalencies : list of equivalent pairs
E.g., as returned by
`~astropy.units.equivalencies.dimensionless_angles`.'

def add_enabled_equivalencies(self, equivalencies):

    equivalencies = _normalize_equivalencies(equivalencies)
    self._equivalencies |= set(equivalencies)
