text: """QM9 functions."""
  import collections as col
  from atom3d.util.formats import *
  
  def qm9_ensembler(sdf_files):
      
      bp = read_sdf(sdf_files)
      df = bp_to_df(bp)
      
      df['subunit'] = df['model']
      df['structure'] = df['model']
      df['ensemble'] = df['model']
  
      ensembles = {}
      subunits = {}
      for mol in df.groupby(['ensemble','model'],as_index=False):
          subunits[mol[0][1]] = mol[1]
      ensembles[None] = subunits
  
      return ensembles
      
  