<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def write_markdown_to_file(self, f):
 """Writes this index to file `f`. The output is formatted as an unordered list. Each list element contains the title of the library, followed by a list of symbols in that library hyperlinked to the corresponding anchor in that library. Args: f: The output file. """

    print("---", file=f)
    print("---", file=f)
    print("<!-- This file is machine generated: DO NOT EDIT! -->", file=f)
    print("", file=f)
    print("# TensorFlow Python reference documentation", file=f)
    print("", file=f)
    fullname_f = lambda name: self._members[name][0]
    anchor_f = lambda name: _get_anchor(self._module_to_name, fullname_f(name))

    for filename, library in self._filename_to_library_map:
      sorted_names = sorted(library.mentioned, key=lambda x: (str.lower(x), x))
      member_names = [n for n in sorted_names if n in self._members]
      # TODO: This is a hack that should be removed as soon as the website code
      # allows it.
      full_filename = self._path_prefix + filename
      links = ["[`%s`](%s#%s)" % (name, full_filename[:-3], anchor_f(name))
               for name in member_names]
      if links:
        print("* **[%s](%s)**:" % (library.title, full_filename[:-3]), file=f)
        for link in links:
          print("  * %s" % link, file=f)
        print("", file=f)