What does the ValueError "Unknown optimizer: Custom>Adam| Adam Optimizer on Raspberry Pi (TensorFlow 2.5.0rc0)" mean?

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The ValueError "Unknown optimizer: Custom>Adam| Adam Optimizer on Raspberry Pi (TensorFlow 2.5.0rc0)" means that the optimizer specified in the code is not recognized by the TensorFlow version installed on the Raspberry Pi. The optimizer in question is likely a custom implementation of the Adam optimizer, but it is not available in the TensorFlow library installed on the Raspberry Pi. Updating the TensorFlow library or specifying a different optimizer may be necessary to resolve this error.