input: Write a python function to preprocess the data by converting it to a numpy array.
  assert type(preprocess_data("data.csv")) == np.ndarray
  assert preprocess_data("data.csv").shape[1] == expected_number_of_columns
output: def preprocess_data(file_path):
      import numpy as np
      import pandas as pd
      
      df = pd.read_csv(file_path)
      return df.to_numpy()