code: def add_namespace_def(self, namespace):
      namespace_def = f"namespace {namespace} {{"
      self.add_code_line(namespace_def)
      self.increase_indent()
  
file_path: m2cgen/m2cgen/interpreters/c_sharp/code_generator.py
imports: from contextlib import contextmanager
  from m2cgen.interpreters.code_generator import CLikeCodeGenerator
label_desc: Use image node_id 3 for calling the CSharpCodeGenerator obj's underlying member method code with example usage: obj.add_namespace_def(namespace) without return types