parameters: (flag_name, default_value, docstring)
docstring: Defines a flag of type 'string'.
  
    Args:
      flag_name: The name of the flag as a string.
      default_value: The default value the flag should take as a string.
      docstring: A helpful message explaining the use of the flag.
docstring_summary: Defines a flag of type 'string'.
docstring_tokens: Defines a flag of type string .
function: def DEFINE_string(flag_name, default_value, docstring):
    """Defines a flag of type 'string'.
  
    Args:
      flag_name: The name of the flag as a string.
      default_value: The default value the flag should take as a string.
      docstring: A helpful message explaining the use of the flag.
    """
    _define_helper(flag_name, default_value, docstring, str)
function_tokens: def DEFINE_string ( flag_name , default_value , docstring ) : _define_helper ( flag_name , default_value , docstring , str )