code: def has_active_subscription(self, plan=None):
  		
  
  		if plan is None:
  			valid_subscriptions = self._get_valid_subscriptions()
  
  			if len(valid_subscriptions) == 0:
  				return False
  			elif len(valid_subscriptions) == 1:
  				return True
  			else:
  				raise TypeError(
  					"plan cannot be None if more than one valid subscription exists for this customer."
  				)
  
  		else:
  			# Convert Plan to id
  			if isinstance(plan, StripeModel):
  				plan = plan.id
  
  			return any(
  				[
  					subscription.is_valid()
  					for subscription in self.subscriptions.filter(plan__id=plan)
  				]
  			)
docs: Checks to see if this customer has an active subscription to the given plan.
  
  		:param plan: The plan for which to check for an active subscription. If plan is None and
  			there exists only one active subscription, this method will check if that subscription
  			is valid. Calling this method with no plan and multiple valid subscriptions for this customer will
  			throw an exception.
  		:type plan: Plan or string (plan ID)
  
  		:returns: True if there exists an active subscription, False otherwise.
  		:throws: TypeError if ``plan`` is None and more than one active subscription exists for this customer.