code: async def get_cred_def_id(self):
          
          cb = create_cb(CFUNCTYPE(None, c_uint32, c_uint32, c_char_p))
          c_handle = c_uint32(self.handle)
          cred_def_id = await do_call('vcx_credentialdef_get_cred_def_id', c_handle, cb)
          return cred_def_id .decode()
docs: Get the ledger ID of the object
  
          Example:
          source_id = 'foobar123'
          schema_name = 'Schema Name'
          payment_handle = 0
          credential_def1 = await CredentialDef.create(source_id, name, schema_id, payment_handle)
          assert await credential_def.get_cred_def_id() == '2hoqvcwupRTUNkXn6ArYzs:3:CL:2471'
          :return: ID string