code: def constant_then(
      rate: float, steps: int, schedule: Iterable[float]
  ) -> Iterable[float]:
      """Yield a constant rate for N steps, before starting a schedule."""
      for i in range(steps):
          yield rate
      for value in schedule:
          yield value
  
file_path: thinc/thinc/schedules.py
imports: from typing import Iterable
  import numpy
  from .config import registry
label_desc: Use image node_id 1 for calling a global function with example usage: constant_then(rate, steps, schedule) without return types