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GraphEvent Objects

@dataclass
class GraphEvent()
A graph event emitted for specific graph events such as start node or end node, and used by the callback to emit user-defined events. Arguments:
  • type (GraphEventType | str): The type of event, can be start_node, end_node, callback, or a custom str.
  • identifier (str): The identifier of the event, this is set typically by a callback handler and can be used to distinguish between different events. For example, a conversation/session ID could be used.
  • token (str | None): The token associated with the event, such as LLM streamed output.
  • params (dict[str, Any] | None): The parameters associated with the event, such as tool call parameters or event metadata.

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encode

def encode(charset: str = "utf-8") -> bytes
Encodes the event as a JSON string, important for compatability with FastAPI and starlette. Arguments:
  • charset (str): The character set to use for encoding the event.

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CallbackProtocol Objects

@runtime_checkable
class CallbackProtocol(Protocol)
Protocol defining the interface for callback handlers.

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Callback Objects

class Callback()
The original callback handler class. Outputs a stream of structured text tokens. It is recommended to use the newer EventCallback handler instead.

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aiter

async def aiter() -> AsyncIterator[str]
Used by receiver to get the tokens from the stream queue. Creates a generator that yields tokens from the queue until the END token is received.

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start_node

async def start_node(node_name: str, active: bool = True)
Starts a new node and emits the start token.

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end_node

async def end_node(node_name: str)
Emits the end token for the current node.

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close

async def close()
Close the stream and prevent further tokens from being added. This will send an END token and set the done flag to True.

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EventCallback Objects

class EventCallback()
The event callback handler class. Outputs a stream of structured text tokens. It is recommended to use the newer EventCallback handler instead.

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__call__

def __call__(token: str | None = None,
             type: GraphEventType | str = GraphEventType.CALLBACK,
             identifier: str | None = None,
             params: dict[str, Any] | None = None)
Builds a GraphEvent object and adds it to the queue.

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acall

async def acall(token: str | None = None,
                type: GraphEventType | str = GraphEventType.CALLBACK,
                identifier: str | None = None,
                params: dict[str, Any] | None = None)
Builds a GraphEvent object and adds it to the queue.

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aiter

async def aiter() -> AsyncIterator[GraphEvent]
Used by receiver to get the tokens from the stream queue. Creates a generator that yields tokens from the queue until the END token is received.

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start_node

async def start_node(node_name: str, active: bool = True)
Starts a new node and emits the start token.

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end_node

async def end_node(node_name: str)
Emits the end token for the current node.

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close

async def close()
Close the stream and prevent further tokens from being added. This will send an END token and set the done flag to True.