input: Write a python function to load a CSV file into a pandas DataFrame.
  assert isinstance(load_csv('dataset.csv'), pd.DataFrame)
  assert not load_csv('non_existent_file.csv').empty
output: def load_csv(file_path):
      import pandas as pd
      try:
          df = pd.read_csv(file_path)
      except FileNotFoundError:
          df = pd.DataFrame()
      return df