rewrite update policy so that additional pins are added and not overwritten

def update_policy(self,defaultHeaders):
		""" rewrite update policy so that additional pins are added and not overwritten """
		if self.inputs is not None:
			for k,v in defaultHeaders.items():
				if k not in self.inputs:
					self.inputs[k] = v
				if k == 'pins':
					self.inputs[k] = self.inputs[k] + defaultHeaders[k]
			return self.inputs
		else:
			return self.inputs