How does the '/creature/plot' endpoint generate a histogram of creature name initials, and what libraries does it use?

The endpoint calls get_all() to retrieve all creatures, then uses collections.Counter to count the first letter of each creature's name. It builds a dictionary mapping each letter A-Z to its count and passes that to plotly.express.histogram with list(letters) as x and the counts as y. The resulting figure is converted to PNG bytes with fig.to_image(format="png") and returned as a FastAPI Response with media_type="image/png". The libraries used are collections.Counter, plotly.express, and fastapi.Response.