'Converts the values of the column in-place from the current
unit to the given unit.
To change the unit associated with this column without
actually changing the data values, simply set the ``unit``
property.
Parameters
new_unit : str or `astropy.units.UnitBase` instance
The unit to convert to.
equivalencies : list of equivalence pairs, optional
A list of equivalence pairs to try if the unit are not
directly convertible.  See :ref:`unit_equivalencies`.
Raises
astropy.units.UnitsError
If units are inconsistent'

def convert_unit_to(self, new_unit, equivalencies=[]):

    if (self.unit is None):
        raise ValueError(u'No    unit    set    on    column')
    self.data[:] = self.unit.to(new_unit, self.data, equivalencies=equivalencies)
    self.unit = new_unit
