returns start time

def get_start_time(self):
        """
        returns start time
        """
        start_time = c_double()
        self.library.get_start_time.argtypes = [POINTER(c_double)]
        self.library.get_start_time.restype = None
        self.library.get_start_time(byref(start_time))
        return start_time.value