code: public RetryTemplateBuilder customPolicy(RetryPolicy policy) {
  		Assert.notNull(policy, "Policy should not be null");
  		Assert.isNull(this.baseRetryPolicy,
  				"You have already selected another retry policy");
  		this.baseRetryPolicy = policy;
  		return this;
  	}
docs: If flexibility of this builder is not enough for you, you can provide your own
  {@link RetryPolicy} via this method.
  <p>
  Invocation of this method does not discard default exception classification rule,
  that is "retry only on {@link Exception} and it's subclasses".
  @param policy will be directly set to resulting {@link RetryTemplate}
  @return this