docstr: Returns the number of independent generators of D_n
docstr_tok: ["Returns","the","number","of","independent","generators","of","D_n"]
code: def basis(self):
      """
      Returns the number of independent generators of D_n
      """
      n = self.n
      return n * (n - 1) / 2
  
file_path: sympy/sympy/liealgebras/type_d.py
imports: from .cartan_type import Standard_Cartan
  from sympy.core.backend import eye
label_desc: Use image node_id 8 for calling the TypeD obj's underlying member method code with example usage: obj.basis() and returns: unknown