docs: def dumps(self, separator='='):
          """
          Convert the mapping to a text string in simple line-oriented
          ``.properties`` format.
  
          If the instance was originally created from a file or string with
          `PropertiesFile.load()` or `PropertiesFile.loads()`, then the output
          will include the comments and whitespace from the original input, and
          any keys that haven't been deleted or reassigned will retain their
          original formatting and multiplicity.  Key-value pairs that have been
          modified or added to the mapping will be reformatted with
          `join_key_value()` using the given separator.  All key-value pairs are
          output in the order they were defined, with new keys added to the end.
  
          .. note::
  
              Serializing a `PropertiesFile` instance with the :func:`dumps()`
              function instead will cause all formatting information to be
              ignored, as :func:`dumps()` will treat the instance like a normal
              mapping.
  
          :param separator: The string to use for separating new or modified keys
              & values.  Only ``" "``, ``"="``, and ``":"`` (possibly with added
              whitespace) should ever be used as the separator.
          :type separator: text string
          :rtype: text string
          """
          s = six.StringIO()
          self.dump(s, separator=separator)
          return s.getvalue()