code: def dynkin_diagram(self):
      diag = "0---0=>=0---0\n"
      diag += "   ".join(str(i) for i in range(1, 5))
      return diag
  
file_path: sympy/sympy/liealgebras/type_f.py
imports: from .cartan_type import Standard_Cartan
  from sympy.core.backend import Matrix, Rational
label_desc: Use image node_id 9 for calling the TypeF obj's underlying member method code with example usage: obj.dynkin_diagram() and returns: diag