input: Write a function to develop a decision tree classifier in Python that predicts the fourth feature from three other features. The function should read a dataset from a CSV file, split the dataset into features and labels, and fit the classifier to the dataset. Return the trained classifier.
  assert decision_tree_classifier("data.csv").predict([[3, 5, 2]]) == [1]
output: import pandas as pd
  from sklearn.tree import DecisionTreeClassifier
  
  def decision_tree_classifier(file_path):
      data = pd.read_csv(file_path)
      X = data.iloc[:, :3]
      y = data.iloc[:, 3]
      clf = DecisionTreeClassifier()
      clf.fit(X, y)
      return clf