input: Write a python function to filter names containing a given substring.
  assert filter_names(["Taylor", "Hilton", "John", "Jack", "Justin"], "J")==["John", "Jack", "Justin"]
  assert filter_names(["Taylor", "Hilton", "John", "Jack", "Justin"], "o")==["John"]
  assert filter_names(["Taylor", "Hilton", "John", "Jack", "Justin"], "T")==["Taylor"]
output: def filter_names(names, substring):
      return [name for name in names if substring in name]