[Python] Cannot initialize variable with None in Indie

I am facing with error with timeframe handling while creating Indie technical indicator.

Error: [internal] cannot initialize tf_choosed with None; in Indie language optionals are explicit, so to make this assignment, you need to declare tf_choosed as indie.Optional[...]
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I think it's in this part of code:

def __init__(self, use_current_tf, tf_custom):
tf_choosed = None # This is causing error
self._out = self.calc_on(SecMain, time_frame=tf_choosed, lookahead=True)


Code:

# indie:lang_version = 5
import math
from indie import indicator, param, sec_context, MainContext, param_ref, color, plot, MutSeriesF
from indie.algorithms import Wma, Ema, Ma


@sec_context
@param_ref('len')
@param_ref('ma_type')
def SecMain(self, len, ma_type):
src = self.close
if ma_type == 'HullMA':
wma_l2 = Wma.new(src, len // 2)[0]
wma_l = Wma.new(src, len)[0]
return Wma.new(MutSeriesF.new(2 * wma_l2 - wma_l), round(math.sqrt(len)))[0]
elif ma_type == 'TEMA':
ema1 = Ema.new(src, len)
ema2 = Ema.new(ema1, len)
ema3 = Ema.new(ema2, len)
return 3 * (ema1[0] - ema2[0]) + ema3[0]
return Ma.new(src, len, ma_type)[0]


@indicator('Ultimate MA - MultiTF', overlay_main_pane=True)
@param.bool('use_current_tf', default=True, title='Use Current Chart Time Frame?')
@param.time_frame('tf_custom', default='1D', title='Use Different Timeframe? Uncheck Box Above')
@param.int('len', default=20, min=1, title='Moving Average Length - LookBack Period')
@param.str('ma_type', default='SMA', options=['SMA', 'EMA', 'WMA', 'HullMA', 'VWMA', 'RMA', 'TEMA'], title='MA algorithm')
@param.bool('cc', default=True, title='Change Color Based On Direction?')
@param.int('smoothe', default=10, min=1, max=10, title='Color Smoothing (1 = No Smoothing)')
@plot.line(line_width=4, title='Multi-Timeframe Moving Avg', id='#plot_0')
class Main(MainContext):
def __init__(self, use_current_tf, tf_custom):
tf_choosed = None
self._out = self.calc_on(SecMain, time_frame=tf_choosed, lookahead=True)
tf_choosed = self.time_frame if use_current_tf else tf_custom


def calc(self, cc, smoothe):
ma_up = self._out[0] >= self._out[smoothe]
ma_down = self._out[0] < self._out[smoothe]

col = color.AQUA
if cc and ma_up:
col = color.LIME
elif cc and ma_down:
col = color.RED

return plot.Line(self._out[0], color=col)


What I did:

• I initially tried setting tf_choosed = None as a default value before the conditional assignment
• I tried to directly use the ternary condition without an intermediate variable

What is the correct way to import and use Optional types?

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