keras/src/optimizers/base_optimizer.py/BaseOptimizer/assign
class BaseOptimizer:    def assign(self, variable, value):
        """Assign a value to a variable.

        This should be used in optimizers instead of `variable.assign(value)` to
        support backend specific optimizations.
        Note that the variable can be a model variable or an optimizer variable;
        it can be a backend native variable or a Keras variable.

        Args:
            variable: The variable to update.
            value: The value to add to the variable.
        """
        variable.assign(value)