code: def _rsqrt(step_number, tail_start, body_value):
      """Computes a tail using a scaled reciprocal square root of step number.
  
      Args:
        step_number: Absolute step number from the start of training.
        tail_start: Step number at which the tail of the curve starts.
        body_value: Value relative to which the tail should be computed.
  
      Returns:
        A learning rate value that falls as the reciprocal square root of the step
        number, scaled so that it joins smoothly with the body of a BodyAndTail
        instance.
      """
      return body_value * (
          math.sqrt(tail_start) / math.sqrt(step_number)
      )
  
file_path: trax/trax/supervised/lr_schedules.py
imports: import math
  import gin
  from trax.fastmath import numpy
label_desc: Use image node_id 5 for calling a global function with example usage: _rsqrt(step_number, tail_start, body_value) and returns: unknown