def list_steps(jobflow_id, options={})
      params = {
        :operation => 'ListSteps',
        :cluster_id => jobflow_id,
      }
      params.merge!(:step_ids => options[:step_ids]) if options[:step_ids]
      params.merge!(:step_states => options[:step_states]) if options[:step_states]
      params.merge!(:marker => options[:marker]) if options[:marker]
      aws_result = @aws_request.submit(params)
      yield aws_result if block_given?
      JSON.parse(aws_result)
    end
def list_steps(jobflow_id, options={})
      params = {
        :operation => 'ListSteps',
        :cluster_id => jobflow_id,
      }
      params.merge!(:step_ids => options[:step_ids]) if options[:step_ids]
      params.merge!(:step_states => options[:step_states]) if options[:step_states]
      params.merge!(:marker => options[:marker]) if options[:marker]
      aws_result = @aws_request.submit(params)
      yield aws_result if block_given?
      JSON.parse(aws_result)
    end
List the steps in a job flow given specified filtering

   emr.list_steps('j-123', {
     :types => ['MASTER', 'CORE', 'TASK'],
     :step_ids => ['ID-1', 'ID-2']
     :step_states => ['PENDING', 'RUNNING', ...]
     :marker => 'marker'                         # Retrieve from a prior call to list_steps
   })

 http://docs.aws.amazon.com/ElasticMapReduce/latest/API/API_ListSteps.html