code: def _dataframe_to_edge_list(df):
      
      cols = df.columns
      if len(cols):
          assert _SRC_VID_COLUMN in cols, "Vertex DataFrame must contain column %s" % _SRC_VID_COLUMN
          assert _DST_VID_COLUMN in cols, "Vertex DataFrame must contain column %s" % _DST_VID_COLUMN
          df = df[cols].T
          ret = [Edge(None, None, _series=df[col]) for col in df]
          return ret
      else:
          return []
docs: Convert dataframe into list of edges, assuming that source and target ids are stored in _SRC_VID_COLUMN, and _DST_VID_COLUMN respectively.