code: def in_base(self, unit_system=None):
          
          us = _sanitize_unit_system(unit_system, self)
          try:
              conv_data = _check_em_conversion(
                  self.units, unit_system=us, registry=self.units.registry
              )
          except MKSCGSConversionError:
              raise UnitsNotReducible(self.units, us)
          if any(conv_data):
              to_units, (conv, offset) = _em_conversion(
                  self.units, conv_data, unit_system=us
              )
          else:
              to_units = self.units.get_base_equivalent(unit_system)
              conv, offset = self.units.get_conversion_factor(to_units, self.dtype)
          new_dtype = np.dtype("f" + str(self.dtype.itemsize))
          conv = new_dtype.type(conv)
          ret = self.v * conv
          if offset:
              ret = ret - offset
          return type(self)(ret, to_units)
docs: Creates a copy of this array with the data in the specified unit
          system, and returns it in that system's base units.
  
          Parameters
          ----------
          unit_system : string, optional
              The unit system to be used in the conversion. If not specified,
              the configured default base units of are used (defaults to MKS).
  
          Examples
          --------
          >>> from unyt import erg, s
          >>> E = 2.5*erg/s
          >>> print(E.in_base("mks"))
          2.5e-07 W