valueError: perplexity must be less than n_samples  #9

My corpus has 49 records, which is not a short text.
No error is reported when T>=6, but an error is reported when T<=5

model = btm.BTM(X, vocab, T=5, M=50, alpha=1, beta=0.01)
model.fit(biterms, iterations=100)

tmp.report(model=model, docs=content_flat)
valueError: perplexity must be less than n_samples

I found that this error is not directly related to the level of perplexity
T=5 perplexity:263.31198210806156
T=6 perplexity:251.15355539215517
the number of records is 49

Name: tmplot
Version: 0.1.0
Name: bitermplus
Version: 0.7.0

This error has caused me a lot of trouble. I look forward to your reply. Thank you.