code: def testLoadMetricsAsDataFrame_Empty(self):
      metrics_for_slices = [
          text_format.Parse(
              """
          slice_key {
             single_slice_keys {
               column: "age"
               float_value: 38.0
             }
             single_slice_keys {
               column: "sex"
               bytes_value: "Female"
             }
           }
           """,
              metrics_for_slice_pb2.MetricsForSlice(),
          ),
      ]
      dfs = dataframe.metrics_as_dataframes(metrics_for_slices)
      self.assertTrue(all(d is None for d in dataclasses.astuple(dfs)))
  
imports: import dataclasses
  import numpy
  import pandas
  import tensorflow
  from tensorflow_model_analysis.experimental import dataframe
  from tensorflow_model_analysis.proto import metrics_for_slice_pb2
  from google.protobuf import text_format
label_desc: Use image node_id 5 for calling the MetricsAsDataFrameTest obj's underlying member method code with example usage: obj.testLoadMetricsAsDataFrame_Empty() without return types