Can't Parse Multiple Transactions in Single 837

[Mythran101]

It appears that one of the forks fixed this problem (cybernescens X12Parser fork), but it has its own issues (can't serialize anything back to X12/XML/HTML in its current state, at least from everything I've thrown at it!).

Multiple transactions in a single 837 file that have the same Hierarchical Loop ID values within the same file, but different transactions (ST) cause an exception due to the way it flattens the Hierarchical Loop into a dictionary, keyed by Hierarchical Loop ID.