input: Write a function to explain the difference between a ``list`` and a ``tuple`` in Python. It should return a string that describes the characteristics of each, including their mutability, syntax, and typical use cases.
  assert explain_list_tuple('list')=='A list in Python is mutable, meaning its contents can be changed. It is surrounded by square brackets and is used when the data needs to be changed.'
  assert explain_list_tuple('tuple')=='A tuple in Python is immutable, meaning its contents cannot be changed. It is surrounded by parentheses and is used when the data is fixed and cannot be changed.'
  assert explain_list_tuple('')=='Please specify either \'list\' or \'tuple\'.'
output: def explain_list_tuple(data_type):
      if data_type == 'list':
          return 'A list in Python is mutable, meaning its contents can be changed. It is surrounded by square brackets and is used when the data needs to be changed.'
      elif data_type == 'tuple':
          return 'A tuple in Python is immutable, meaning its contents cannot be changed. It is surrounded by parentheses and is used when the data is fixed and cannot be changed.'
      else:
          return 'Please specify either \'list\' or \'tuple\'.'