langchain/tools/file_management/read.py/ReadFileTool/_run
class ReadFileTool:    def _run(
        self,
        file_path: str,
        run_manager: Optional[CallbackManagerForToolRun] = None,
    ) -> str:
        try:
            read_path = self.get_relative_path(file_path)
        except FileValidationError:
            return INVALID_PATH_TEMPLATE.format(arg_name="file_path", value=file_path)
        if not read_path.exists():
            return f"Error: no such file or directory: {file_path}"
        try:
            with read_path.open("r", encoding="utf-8") as f:
                content = f.read()
            return content
        except Exception as e:
            return "Error: " + str(e)