def canonical_before_tool_callbacks(
      self,
  ) -> list[BeforeToolCallback]:
    """The resolved self.before_tool_callback field as a list of BeforeToolCallback.

    This method is only for use by Agent Development Kit.
    """
    if not self.before_tool_callback:
      return []
    if isinstance(self.before_tool_callback, list):
      return self.before_tool_callback
    return [self.before_tool_callback]
The resolved self.before_tool_callback field as a list of BeforeToolCallback.

    This method is only for use by Agent Development Kit.
    
src/google/adk/agents/llm_agent.py