Reads and loads in to `self.obj` a single key or all keys from source

        :param filename: Optional filename to load
        :param key: if provided load a single key
        :param silent: if load erros should be silenced

def load(self, filename=None, key=None, silent=True):
        """
        Reads and loads in to `self.obj` a single key or all keys from source

        :param filename: Optional filename to load
        :param key: if provided load a single key
        :param silent: if load erros should be silenced
        """
        filename = filename or self.obj.get(self.identifier.upper())
        if not filename:
            return

        if not isinstance(filename, (list, tuple)):
            split_files = ensure_a_list(filename)
            if all([f.endswith(self.extensions) for f in split_files]):  # noqa
                files = split_files  # it is a ['file.ext', ...]
            else:  # it is a single config as string
                files = [filename]
        else:  # it is already a list/tuple
            files = filename

        self.obj._loaded_files.extend(files)

        # add the [default] env
        env_list = [self.obj.get("DEFAULT_ENV_FOR_DYNACONF")]

        # compatibility with older versions that still uses [dynaconf] as
        # [default] env
        global_env = self.obj.get("ENVVAR_PREFIX_FOR_DYNACONF") or "DYNACONF"
        if global_env not in env_list:
            env_list.append(global_env)

        # add the current [env]
        if self.env not in env_list:
            env_list.append(self.env)

        # add the [global] env
        env_list.append("GLOBAL")

        # load all envs
        self._read(files, env_list, silent, key)