code: @Override
      public GetContextKeysForCustomPolicyResult getContextKeysForCustomPolicy(GetContextKeysForCustomPolicyRequest request) {
          request = beforeClientExecution(request);
          return executeGetContextKeysForCustomPolicy(request);
      }
docs: <p>
  Gets a list of all of the context keys referenced in the input policies. The policies are supplied as a list of
  one or more strings. To get the context keys from policies associated with an IAM user, group, or role, use
  <a>GetContextKeysForPrincipalPolicy</a>.
  </p>
  <p>
  Context keys are variables maintained by AWS and its services that provide details about the context of an API
  query request. Context keys can be evaluated by testing against a value specified in an IAM policy. Use
  <code>GetContextKeysForCustomPolicy</code> to understand what key names and values you must supply when you call
  <a>SimulateCustomPolicy</a>. Note that all parameters are shown in unencoded form here for clarity but must be
  URL encoded to be included as a part of a real HTML request.
  </p>
  
  @param getContextKeysForCustomPolicyRequest
  @return Result of the GetContextKeysForCustomPolicy operation returned by the service.
  @throws InvalidInputException
  The request was rejected because an invalid or out-of-range value was supplied for an input parameter.
  @sample AmazonIdentityManagement.GetContextKeysForCustomPolicy
  @see <a href="http://docs.aws.amazon.com/goto/WebAPI/iam-2010-05-08/GetContextKeysForCustomPolicy"
  target="_top">AWS API Documentation</a>