Optimize sequence_to_text function with join method

[vivekmaru36]

This pull request modifies the init.py file to optimize the sequence_to_text function within the module. The update enhances the function's efficiency by replacing manual iteration and concatenation with the more efficient join method for string construction.

Changes:

Optimized sequence_to_text function for improved performance. Incorporated the join method for string concatenation. Introduced _id_to_symbol parameter for enhanced symbol lookup efficiency.

Purpose:

Enhancing the performance of the sequence_to_text function allows for more efficient text decoding from sequences of IDs, benefiting overall model operations and processing.

[Zengyi-Qin]

Sorry the for loop still exists. No performance gain from this PR