Add missing model context attribute (#4848) #12

Job	Run time
lint	51s
format	1m 1s
mypy (./packages/autogen-core)	2m 2s
mypy (./packages/autogen-magentic-one)	1m 16s
pyright (./packages/autogen-core)	1m 0s
mypy (./packages/agbench)	57s
pyright (./packages/autogen-magentic-one)	58s
mypy (./packages/autogen-ext)	1m 52s
pyright (./packages/agbench)	54s
mypy (./packages/autogen-agentchat)	1m 15s
check-proto-changes-python	1m 8s
pyright (./packages/autogen-ext)	1m 5s
pyright (./packages/autogen-agentchat)	55s
docs (./packages/autogen-core)	1m 32s
docs-example-check (./packages/autogen-core)	2m 29s
test (./packages/autogen-core)	55s
test (./packages/autogen-magentic-one)	1m 23s
test (./packages/autogen-ext)	2m 48s
test (./packages/autogen-agentchat)	1m 9s
	25m 30s

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