input: Write a function to load a CSV file into a pandas DataFrame.
  assert load_data('sample.csv').shape==(10,5)  # Assuming 'sample.csv' has 10 rows and 5 columns
  assert isinstance(load_data('sample.csv'), pd.DataFrame)
output: def load_data(file_path):
      import pandas as pd
      return pd.read_csv(file_path)