code: def test_pipeline_builder_merge_single_node():
      builder_a = PipelineBuilder().add_sequence("operation_a")
      builder_b = PipelineBuilder().add_sequence("operation_f")
      builder_ab = PipelineBuilder().add_sequence(
          "operation_a", "operation_f"
      )
  
      assert builders_same(
          builder_ab, merge_pipeline_builders(builder_a, builder_b)
      )
  
imports: from copy import copy
  from fedot.core.pipelines.pipeline_builder import PipelineBuilder, merge_pipeline_builders
  from fedot.core.pipelines.node import PipelineNode
  from fedot.core.pipelines.pipeline import Pipeline
  from test.unit.dag.test_graph_utils import graphs_same
label_desc: Use image node_id 9 for calling a global function with example usage: test_pipeline_builder_merge_single_node() without return types