Hummingbird and Butterfly Gardening: Is this a senna/cassia seedling?, 1 by beckygardener

beckygardener wrote:
I posted this in the plant ID forum, but thought I would also post the photo here as well.

I have several of these popping up in my seed garden beds. I do NOT remember planting any cassia seeds. So .... my question ..... is this a keeper for my garden beds or a weed I should pull? It is very fast growing, has small yellow flowers popping up at the point where the leaves branch out from the stalk. The flowers almost look like a sweet pea flower. As you can barely see in this photo. (I don't have a macro lense for my camera, so this is the best I could get.)

Help! Does anyone recognize what this plant is?