code: def get_newcommand_macros(tex_source):
      r
      macros = {}
      command = LatexCommand(
          'newcommand',
          {'name': 'name', 'required': True, 'bracket': '{'},
          {'name': 'content', 'required': True, 'bracket': '{'})
  
      for macro in command.parse(tex_source):
          macros[macro['name']] = macro['content']
  
      return macros
docs: r"""Get all ``\newcommand`` macro definition from TeX source.
  
      Parameters
      ----------
      tex_source : `str`
          TeX source content.
  
      Returns
      -------
      macros : `dict`
          Keys are macro names (including leading ``\``) and values are the
          content (as `str`) of the macros.
  
      Notes
      -----
      ``\newcommand`` macros with arguments are not supported.