def literal_symbol(literal):
 if ((literal is True) or (literal is False)):
  return literal
 try:
  if literal.is_Symbol:
   return literal
  if literal.is_Not:
   return literal_symbol(literal.args[0])
  else:
   raise ValueError
 except (AttributeError, ValueError):
  raise ValueError('Argument must be a boolean literal.')

def literal_symbol ( literal ) : if ( ( literal is True ) or ( literal is False ) ) : return literal try : if literal . is_Symbol : return literal if literal . is_Not : return literal_symbol ( literal . args [ 0 ] ) else : raise ValueError except ( AttributeError , ValueError ) : raise ValueError ( 'Argument must be a boolean literal.' )
the symbol in this literal .