class_docstr: This class contains the information about
  the A series of simple Lie algebras.
  ====
docstr: Returns the highest weight root for A_n
docstr_tok: ["Returns","the","highest","weight","root","for","A_n"]
code: def highest_root(self):
      """
      Returns the highest weight root for A_n
      """
  
      return self.basic_root(0, self.n)
  
file_path: sympy/sympy/liealgebras/type_a.py
imports: from sympy.liealgebras.cartan_type import Standard_Cartan
  from sympy.core.backend import eye
label_desc: Use image node_id 6 for calling the TypeA obj's underlying member method code with example usage: obj.highest_root() and returns: self