toString method
A string representation of this object.
Some classes have a default textual representation,
often paired with a static parse function (like int.parse).
These classes will provide the textual representation as
their string representation.
Other classes have no meaningful textual representation
that a program will care about.
Such classes will typically override toString to provide
useful information when inspecting the object,
mainly for debugging or logging.
Implementation
@override
String toString() {
final parts = <String>[];
if (promptTokens != null) parts.add('prompt: $promptTokens');
if (completionTokens != null) parts.add('completion: $completionTokens');
if (reasoningTokens != null) parts.add('reasoning: $reasoningTokens');
if (totalTokens != null) parts.add('total: $totalTokens');
return 'UsageInfo(${parts.join(', ')})';
}