Enhance tfjs2keras integration test

[caisq]

Enhance tfjs2keras integration test

Previously only the loading of model topology was tested.

This PR adds the test for the loading of weight values. In addition,
this PR lets each model run its predict() method using some
randomly generated data. The input data and the prediction() outputs
are saved to disk from TensorFlow.js. On the Python side, the
input tensors are loaded and used to invoke the loaded models.
The (near) equality of the outputs from Python and from those from
TensorFlow.js is asserted on for each model.

DEV

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This change is 

[davidsoergel]

Reviewable status: 0 of 1 approvals obtained (waiting on @caisq, @nsthorat, and @dsmilkov)

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integration_tests/tfjs2keras/tfjs_save.ts, line 18 at r1 (raw file):

/**
 * Generate random input(s) get predict() output(s) and save them, along with

Nit: commas and wording, e.g. "Generate random input(s), get predict() output(s), and save both along with the model"

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integration_tests/tfjs2keras/tfjs_save.ts, line 42 at r1 (raw file):

    if (inputShape.indexOf(null) !== -1) {
      throw new Error(
          `It is assume that the only the first dimension of the tensor ` +

nit: assumed

[davidsoergel]

Reviewed 5 of 5 files at r1.
Reviewable status: 0 of 1 approvals obtained (waiting on @caisq, @nsthorat, and @dsmilkov)

[caisq]

Reviewable status: complete! 1 of 1 approvals obtained (waiting on @nsthorat and @dsmilkov)

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integration_tests/tfjs2keras/tfjs_save.ts, line 18 at r1 (raw file):

Previously, davidsoergel (David Soergel) wrote…

Nit: commas and wording, e.g. "Generate random input(s), get predict() output(s), and save both along with the model"

Done.

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integration_tests/tfjs2keras/tfjs_save.ts, line 42 at r1 (raw file):

Previously, davidsoergel (David Soergel) wrote…

nit: assumed

Done.

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[caisq]

@googlebot Ignore CLA issue. It is me with a different email address.