Pass tasks into load_sdf_files so we can extract tasks from .sdf

  def __init__(self, tasks, clean_mols=False, **kwargs):

    super(SDFLoader, self).__init__(tasks, **kwargs)

    self.clean_mols = clean_mols

    self.tasks = tasks

    self.smiles_field = "smiles"

    self.mol_field = "mol"

    self.id_field = "smiles"

  def get_shards(self, input_files, shard_size):

    """Defines a generator which returns data for each shard"""

    return load_sdf_files(input_files, self.clean_mols)

    return load_sdf_files(input_files, self.clean_mols, self.tasks)

  def featurize_shard(self, shard):

    """Featurizes a shard of an input dataframe."""