How to add authentication (e.g., API key) when using Python A2A client?

[magicbrighter]

Hi team,

I'm trying to use the Python A2A client to interact with an A2A-compatible agent endpoint that requires authentication via an API key. For example, the endpoint can be accessed via curl like this:

curl 'https://mcp.amap.com/a2a/agent/agent_card/.well-known/agent.json' \
  -H 'key: {your-developer-api-key}'

However, I don't see a straightforward way to pass custom headers (like the key header above) when initializing or using the A2A client in Python.

Could you please provide guidance or an example on how to include authentication headers (such as an API key) when making requests through the Python A2A library?

Thanks in advance!