Add back usage.tokens

Author: mkozakov

src/cohere/types/usage.py

@@ -5,9 +5,13 @@
 import pydantic
 from ..core.pydantic_utilities import IS_PYDANTIC_V2
 from ..core.unchecked_base_model import UncheckedBaseModel
+from .usage_billed_units import UsageBilledUnits
+from .usage_tokens import UsageTokens
 
 
 class Usage(UncheckedBaseModel):
+    billed_units: typing.Optional[UsageBilledUnits] = None
+    tokens: typing.Optional[UsageTokens] = None
     cached_tokens: typing.Optional[float] = pydantic.Field(default=None)
     """
     The number of prompt tokens that hit the inference cache.