fix encode

[BossPi]

Before submitting

• Lint code. If there are lint issues, please format the code first.

# Install and register `pre-commit` in the project folder
pip install pre-commit && pre-commit install

# Process previous code files separately
pre-commit run --file XXXX.py

• Add test cases into tests folder. If there are codecov issues, please add tests cases first.

PR types

PR changes

Description

在encode处理messages时，处理连续出现的同一角色内容的情况，特别是assistant+function的情况

[paddle-bot]

Thanks for your contribution!

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 12 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (develop@0bb16af). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
paddleformers/datasets/template/template.py	0.00%	12 Missing ⚠️

❌ Your patch status has failed because the patch coverage (0.00%) is below the target coverage (75.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             develop    #3113   +/-   ##
==========================================
  Coverage           ?   36.02%           
==========================================
  Files              ?      385           
  Lines              ?    69280           
  Branches           ?        0           
==========================================
  Hits               ?    24960           
  Misses             ?    44320           
  Partials           ?        0           

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