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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def validate_data_files(problem, data_files, min_size):
 """Validate presence and minimum size of files."""

  # Check that all files are present
  data_dir = os.path.split(data_files[0])[0]
  out_filepaths = problem.out_filepaths(data_dir)
  missing_filepaths = set(out_filepaths) - set(data_files)
  if missing_filepaths:
    tf.logging.error("Missing %d data files", len(missing_filepaths))

  # Check that each file is at least 100M
  too_small = []
  for data_file in data_files:
    length = get_length(data_file)
    if length < min_size:
      too_small.append(data_file)
  if too_small:
    tf.logging.error("%d files too small", len(too_small))

  bad_files = too_small + list(missing_filepaths)
  return bad_files