def __init__(self, *args):
"""
Construct calculator.
Calls the superclass constructor and then initializes a
Heterodyne ITC object.
"""
super(HeterodyneCalculator, self).__init__(*args)
self.itc = HeterodyneITC()
# Determine which combinations of mapping and switching modes
# are allowed.
valid_modes = self.itc.get_valid_modes()
self.map_modes = OrderedDict(
((map_code,
map_mode._replace(sw_modes=[
sw_code for (sw_code, sw_mode) in self.switch_modes.items()
if (map_mode.id, sw_mode.id) in valid_modes
])) for (map_code, map_mode) in self._map_modes.items()))
