[compat] fix FusedDSAIndexerLoss compat mcore<0.19

[Jintao-Huang]

No description provided.

[gemini-code-assist]

Code Review

This pull request introduces a version check for megatron.core to conditionally pass the calculate_per_token_loss parameter to FusedDSAIndexerLoss.apply only when using version 0.19.0rc0 or newer. The review feedback suggests using getattr when accessing calculate_per_token_loss from self.config to make the code more robust against potential AttributeErrors.

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[gemini-code-assist]

Using getattr(self.config, 'calculate_per_token_loss', False) is safer and more robust than direct attribute access. This prevents potential AttributeError if self.config is a mock object in unit tests or a custom configuration class that does not define calculate_per_token_loss.

Suggested change

	kwargs['calculate_per_token_loss'] = self.config.calculate_per_token_loss
	kwargs['calculate_per_token_loss'] = getattr(self.config, 'calculate_per_token_loss', False)