code: def _read_offset_df(file, trait):
      df = (
          pd.melt(pd.read_table(file, sep=r"\s+"), id_vars=["FID_IID"])
          .rename(
              columns={
                  "FID_IID": "contigName",
                  "variable": "FID_IID",
                  "value": trait,
              }
          )
          .astype({"FID_IID": "str", "contigName": "str"})
      )
      df[["FID", "IID"]] = df.FID_IID.str.split("_", expand=True)
      return (
          df.sort_values(by=["FID", "IID"])
          .drop(columns=["FID", "IID"])
          .set_index(["FID_IID", "contigName"])
      )
  
file_path: glow/python/glow/gwas/tests/functions.py
imports: import glow.functions
  import numpy
  import pandas
  from pandas.testing import assert_frame_equal
label_desc: Use image node_id 2 for calling a global function with example usage: _read_offset_df(file, trait) and returns: df