code: def expand(self, v):
          
          if not is_measure(v) or v['type'] not in ['baseline',
                                                    'position', 'uvw']:
              raise TypeError("Can only expand baselines, positions, or uvw")
          vw = v.copy()
          vw['type'] = "uvw"
          vw['refer'] = "J2000"
          outm = _measures.expand(self, vw)
          outm['xyz'] = dq.quantity(outm['xyz'])
          outm['measure']['type'] = v['type']
          outm['measure']['refer'] = v['refer']
          return outm
docs: Calculates the differences between a series of given measure values:
          it calculates baseline values from position values.
  
          :params v: a measure (of type 'baseline', 'position' or 'uvw')
          :returns: a `dict` with the value for key `measures` being a measure
                    and the value for key `xyz` a quantity containing the
                    differences.
  
          Example::
  
              >>> from casacore.quanta import quantity
              >>> x = quantity([10,50],'m')
              >>> y = quantity([20,100],'m')
              >>> z = quantity([30,150],'m')
              >>> sb = dm.baseline('itrf', x, y, z)
              >>> out = dm.expand(sb)
              >>> print out['xyz']
              [40.000000000000014, 80.0, 120.0] m