Function builtin_parent_env_set 

fn builtin_parent_env_set(
    args: &[RValue],
    _: &[(String, RValue)],
) -> Result<RValue, RError>

Set the parent (enclosing) environment.

This is a replacement function: parent.env(e) <- value sets the parent of environment e to value.

@param env environment whose parent to change @param value new parent environment @return the modified environment (invisibly)