docs: def initialize_period(self, period=None):
          """Initialize the period of BF.
  
          :period: datetime.datetime for setting the period explicity.
          """
          if not period:
              self.current_period = dt.datetime.now()
          else:
              self.current_period = period
          self.current_period = dt.datetime(self.current_period.year, self.current_period.month, self.current_period.day)
          self.date = self.current_period.strftime("%Y-%m-%d")