code: def edges():
      # Four edges originating from the center node and connected to each
      # corner
      edges_df = pd.DataFrame(
          {
              "id": np.arange(4),
              "source": np.zeros(4, dtype=int),
              "target": np.arange(1, 5),
          }
      )
      edges_df.set_index("id")
      return edges_df
  
file_path: datashader/datashader/tests/benchmarks/test_bundling.py
imports: import pytest
  import numpy
  import pandas
  from datashader.bundling import directly_connect_edges, hammer_bundle
  from datashader.layout import circular_layout, forceatlas2_layout, random_layout
label_desc: Use image node_id 2 for calling a global function with example usage: edges() and returns: edges_df