code: def get_global_namespace(decls):
      
      found = [
          decl for decl in scopedef.make_flatten(decls) if decl.name == '::' and
          isinstance(decl, namespace_t)]
      if len(found) == 1:
          return found[0]
      raise RuntimeError("Unable to find global namespace.")
docs: Get the global namespace (::) from a declaration tree.
  
      Args:
          decls (list[declaration_t]): a list of declarations
  
      Returns:
          namespace_t: the global namespace_t object (::)