class_docstr: RMSProp optimizer.
  
  Uses optimizer weights ("slots") to maintain a root-mean-square exponentially
  decaying average of gradients from prior training batches.
code: def init(self, weights):
      return jnp.ones_like(weights)
  
imports: from trax.fastmath import numpy
  from trax.optimizers import base
label_desc: Use image node_id 2 for calling the RMSProp obj's underlying member method code with example usage: obj.init(weights) and returns: jnp