Method AdjustGradients

Adjusts gradients according to learner params. Args: var_grads: a `.NestedMap` whose values are (var, grad) pairs. gradient_mask: if not None, a dict mapping variable names to a 0/1 scalar. gradient_adjuster: if not None, a function that mutates a given var_grads. Returns

(self,
                      var_grads,
                      gradient_mask=None,
                      gradient_adjuster=None)