Shortcut around __init__ for internal use when we want to skip
        costly validation

def _construct_direct(cls, variables, coord_names, dims, attrs=None,
                          indexes=None, encoding=None, file_obj=None):
        """Shortcut around __init__ for internal use when we want to skip
        costly validation
        """
        obj = object.__new__(cls)
        obj._variables = variables
        obj._coord_names = coord_names
        obj._dims = dims
        obj._indexes = indexes
        obj._attrs = attrs
        obj._file_obj = file_obj
        obj._encoding = encoding
        obj._initialized = True
        return obj