class_docstr: This class contains the information about
  the A series of simple Lie algebras.
  ====
code: def dynkin_diagram(self):
      n = self.n
      diag = "---".join("0" for i in range(1, n + 1)) + "\n"
      diag += "   ".join(str(i) for i in range(1, n + 1))
      return diag
  
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 11 for calling the TypeA obj's underlying member method code with example usage: obj.dynkin_diagram() and returns: diag