input: Write a python function to load a CSV file and extract features and target for a machine learning model.
  assert extract_features_target('stocks.csv')== (features_array, target_array)
output: import numpy as np
  import pandas as pd
  
  def extract_features_target(csv_file):
      df = pd.read_csv(csv_file)
      features = df.drop('target', axis=1).values
      target = df['target'].values
      return features, target