code: def _validate_format(self, format):
      if format not in self.FORMAT_VALUES:
          msg = f"unknown format type {format}, must be one of {self.FORMAT_VALUES}"
          raise ValueError(msg)
  
imports: import os
  import numpy
  from numpy import asarray, real, imag, conj, zeros, ndarray, concatenate, ones, can_cast
  from scipy.sparse import coo_matrix, issparse
label_desc: Use image node_id 8 for calling the MMFile obj's underlying member method code with example usage: obj._validate_format(format) without return types