in src/agents/usage.py [0:0]
def add(self, other: "Usage") -> None:
self.requests += other.requests if other.requests else 0
self.input_tokens += other.input_tokens if other.input_tokens else 0
self.output_tokens += other.output_tokens if other.output_tokens else 0
self.total_tokens += other.total_tokens if other.total_tokens else 0