"""Parses the score from a given grade output string.

This function searches through each line of the input string for a line containing the word "score". It then attempts to extract a JSON-like object from that line and parse it to retrieve the score. The function tries multiple methods in sequence: JSON parsing, evaluating the string as a dictionary, and finally using regex to extract the last number in the string.

Args:
    grade_stdout (str): A string containing the grade output, typically from a grading system.

Returns:
    Optional[float]: The parsed score as a float if successful, otherwise None.
"""
You should write code starting with:
import re
import json
from typing import Optional

def _parsing_score(grade_stdout: str) -> Optional[float]:
    # TODO: Implement this function
    pass

