code: def baseline(self, rf='', v0='0..', v1='', v2='', off=None):
          
          loc = {'type': "baseline", 'refer': rf}
          loc['m0'] = dq.quantity(v0)
          loc['m1'] = dq.quantity(v1)
          loc['m2'] = dq.quantity(v2)
          if is_measure(off):
              if not off['type'] == "doppler":
                  raise TypeError('Illegal offset type specified.')
              loc["offset"] = off
          return self.measure(loc, rf)
docs: Defines a baselin measure. It has to specify a reference code, uvw
          quantity values (see introduction for the action on a scalar quantity
          with either a vector or scalar value, and when a vector of quantities
          is given), and optionally it can specify an offset, which in itself
          has to be a baseline.
  
          :param rf: reference code string; Allowable reference
                     codes are: *ITRF* and :meth:`direction` codes
                     Note that additional ones may become available. Check with::
  
                         dm.list_codes(dm.baseline())
  
  
          :param v0: longitude or x as quantity or string
          :param v1: latitude or y as quantity or string
          :param v2: height or z as quantity or string
          :param off: an optional offset measure of same type