def str_replace(self, path: Path, old_str: str, new_str: str | None):
        """Implement the str_replace command, which replaces old_str with new_str in the file content"""
        # Read the file content
        file_content = self.read_file(path).expandtabs()
        old_str = old_str.expandtabs()
        new_str = new_str.expandtabs() if new_str is not None else ""

        # Check if old_str is unique in the file
        occurrences = file_content.count(old_str)
        if occurrences == 0:
            raise ToolError(
                f"No replacement was performed, old_str `{old_str}` did not appear verbatim in {path}."
            )
        elif occurrences > 1:
            file_content_lines = file_content.split("\n")
            lines = [
                idx + 1
                for idx, line in enumerate(file_content_lines)
                if old_str in line
            ]
            raise ToolError(
                f"No replacement was performed. Multiple occurrences of old_str `{old_str}` in lines {lines}. Please ensure it is unique"
            )

        # Replace old_str with new_str
        new_file_content = file_content.replace(old_str, new_str)

        # Write the new content to the file
        self.write_file(path, new_file_content)

        # Save the content to history
        self._file_history[path].append(file_content)

        # Create a snippet of the edited section
        replacement_line = file_content.split(old_str)[0].count("\n")
        start_line = max(0, replacement_line - SNIPPET_LINES)
        end_line = replacement_line + SNIPPET_LINES + new_str.count("\n")
        snippet = "\n".join(new_file_content.split("\n")[start_line : end_line + 1])

        # Prepare the success message
        success_msg = f"The file {path} has been edited. "
        success_msg += self._make_output(
            snippet, f"a snippet of {path}", start_line + 1
        )
        success_msg += "Review the changes and make sure they are as expected. Edit the file again if necessary."

        return CLIResult(output=success_msg)
Implement the str_replace command, which replaces old_str with new_str in the file content
src/upsonic/server/level_utilized/cu/edit.py