ai-agent-book 精选快照（<2MB 代码与文档，来自 github.com/bojieli/ai-agent-book）

chapter9/browser-use-rpa/browser-use/browser_use/llm/google/serializer.py

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+import base64
+
+from google.genai.types import Content, ContentListUnion, Part
+
+from browser_use.llm.messages import (
+	AssistantMessage,
+	BaseMessage,
+	SystemMessage,
+	UserMessage,
+)
+
+
+class GoogleMessageSerializer:
+	"""Serializer for converting messages to Google Gemini format."""
+
+	@staticmethod
+	def serialize_messages(
+		messages: list[BaseMessage], include_system_in_user: bool = False
+	) -> tuple[ContentListUnion, str | None]:
+		"""
+		Convert a list of BaseMessages to Google format, extracting system message.
+
+		Google handles system instructions separately from the conversation, so we need to:
+		1. Extract any system messages and return them separately as a string (or include in first user message if flag is set)
+		2. Convert the remaining messages to Content objects
+
+		Args:
+		    messages: List of messages to convert
+		    include_system_in_user: If True, system/developer messages are prepended to the first user message
+
+		Returns:
+		    A tuple of (formatted_messages, system_message) where:
+		    - formatted_messages: List of Content objects for the conversation
+		    - system_message: System instruction string or None
+		"""
+
+		messages = [m.model_copy(deep=True) for m in messages]
+
+		formatted_messages: ContentListUnion = []
+		system_message: str | None = None
+		system_parts: list[str] = []
+
+		for i, message in enumerate(messages):
+			role = message.role if hasattr(message, 'role') else None
+
+			# Handle system/developer messages
+			if isinstance(message, SystemMessage) or role in ['system', 'developer']:
+				# Extract system message content as string
+				if isinstance(message.content, str):
+					if include_system_in_user:
+						system_parts.append(message.content)
+					else:
+						system_message = message.content
+				elif message.content is not None:
+					# Handle Iterable of content parts
+					parts = []
+					for part in message.content:
+						if part.type == 'text':
+							parts.append(part.text)
+					combined_text = '\n'.join(parts)
+					if include_system_in_user:
+						system_parts.append(combined_text)
+					else:
+						system_message = combined_text
+				continue
+
+			# Determine the role for non-system messages
+			if isinstance(message, UserMessage):
+				role = 'user'
+			elif isinstance(message, AssistantMessage):
+				role = 'model'
+			else:
+				# Default to user for any unknown message types
+				role = 'user'
+
+			# Initialize message parts
+			message_parts: list[Part] = []
+
+			# If this is the first user message and we have system parts, prepend them
+			if include_system_in_user and system_parts and role == 'user' and not formatted_messages:
+				system_text = '\n\n'.join(system_parts)
+				if isinstance(message.content, str):
+					message_parts.append(Part.from_text(text=f'{system_text}\n\n{message.content}'))
+				else:
+					# Add system text as the first part
+					message_parts.append(Part.from_text(text=system_text))
+				system_parts = []  # Clear after using
+			else:
+				# Extract content and create parts normally
+				if isinstance(message.content, str):
+					# Regular text content
+					message_parts = [Part.from_text(text=message.content)]
+				elif message.content is not None:
+					# Handle Iterable of content parts
+					for part in message.content:
+						if part.type == 'text':
+							message_parts.append(Part.from_text(text=part.text))
+						elif part.type == 'refusal':
+							message_parts.append(Part.from_text(text=f'[Refusal] {part.refusal}'))
+						elif part.type == 'image_url':
+							# Handle images
+							url = part.image_url.url
+
+							# Format: data:image/png;base64,<data>
+							header, data = url.split(',', 1)
+							# Decode base64 to bytes
+							image_bytes = base64.b64decode(data)
+
+							# Add image part
+							image_part = Part.from_bytes(data=image_bytes, mime_type='image/png')
+
+							message_parts.append(image_part)
+
+			# Create the Content object
+			if message_parts:
+				final_message = Content(role=role, parts=message_parts)
+				# for some reason, the type checker is not able to infer the type of formatted_messages
+				formatted_messages.append(final_message)  # type: ignore
+
+		return formatted_messages, system_message