Dog Black

What does the black dog in “The Worn Path” symbolize?

I have to write an essay on the symbols in this short story and one of the symbols i have to write about is the black dog. My teacher told me that the dog symbolizes African Americans holding each other back. I wrote this in my essay and a little more but then my teacher told me to expand on this more and I don’t know what else to put in it.
Any ideas?

its very complicated but if you read it carfully it stands for a black dog