code: def test_mostly_nan_values():
      x = np.empty(shape=1000)
      x[:] = np.NaN
      x[:3] = 1
      df = pd.DataFrame({"mostly_empty": x})
      types = detect_types(df)
      assert types.useless.mostly_empty
  
imports: import os
  import pytest
  import random
  import string
  import warnings
  import numpy
  import pandas
  from sklearn.datasets import load_iris, load_digits
  from sklearn.model_selection import train_test_split
  from sklearn.pipeline import make_pipeline
  from sklearn.linear_model import LogisticRegression
  from dabl.preprocessing import USELESS_TYPES, detect_types, EasyPreprocessor, DirtyFloatCleaner, clean, _FLOAT_REGEX, _float_matching, detect_type_series
  from dabl.utils import data_df_from_bunch
  from dabl.datasets import load_titanic
  from dabl import plot
label_desc: Use image node_id 29 for calling a global function with example usage: test_mostly_nan_values() without return types