The learning_rate in TensorFlow code is the sum learning rate of a batch or the learning rate of a data?
It is the learning rate that you set on the optimizer for your problem. It requires a fair bit of experimentation to figure out what learning rate works best for your problem. It is a more of an art than a science, though there exists heuristics on an optimal range of values to select from.
For most problems, the default learning rate should be a good starting point.