keras/src/dtype_policies/dtype_policy.py/DTypePolicy/variable_dtype
class DTypePolicy:    def variable_dtype(self):
        """The variable dtype of this policy.

        This is the dtype layers will create their variables in, unless a layer
        explicitly chooses a different dtype. If this is different than
        `DTypePolicy.compute_dtype`, Layers will cast variables to
        the compute dtype to avoid type errors.

        Variable regularizers are run in the variable dtype, not the compute
        dtype.

        Returns:
            The variable dtype of this policy, as a string.
        """
        return self._variable_dtype