code: def in_hours(self, office=None, when=None):
  		
  
  		if when == None:
  			when = datetime.now(tz=utc)
  
  		if office == None:
  			for office in self.offices.itervalues():
  				if office.in_hours(when):
  					return True
  
  			return False
  
  		else:
  			# check specific office
  			return self.offices[office].in_hours(when)
docs: Finds if it is business hours in the given office.
  
  		:param office: Office ID to look up, or None to check if any office is in business hours.
  		:type office: str or None
  
  		:param datetime.datetime when: When to check the office is open, or None for now.
  
  		:returns: True if it is business hours, False otherwise.
  		:rtype: bool
  
  		:raises KeyError: If the office is unknown.