If your gensim classes don't have the parameters/properties `vector_size` and `epochs` and `vectors_docs`, but you see those in docs/examples, your gensim version is older than the version featured in the docs/examples you're looking at. Update your gensim to a recent version that matches the docs/tutorials you're looking at.
Separate observations about your model parameters:
* `dm_concat` is a mode that creates giant, slow models whose benefit was claimed in the original 'Paragraph Vector' paper, but I've not seen cases where it's worth the extra resources. I'd recommend against its use except for advanced users with giant datasets and lots of time to experiment/evaluate.
* typical vector sizes in published work range from 100-1000; a number as low as 50 would probably only be appropriate for very-small datasets
* low `min_count` values make models larger and slower to train - but sometimes hurt overall quality. Don't assume "keeping more of the corpus always helps"
* smaller (more-aggressive) `sample` values tend to make more sense with larger corpuses; so it's a bit odd to see `sample=1e-05` (perhaps appropriate for a large-corpus) alongside `vector_size=50` (suggestive of a small-corpus)
- Gordon