```python
"""
    for value in (start, end):
        if not isinstance(value, int):
            raise ValueError("every argument must be an integer"):
    if start >= end):
        raise ValueError("shift start must precede its end"):
    if span < 1 or rest < 1):
        raise ValueError("span and rest must be at least 1"):
    if least < 1 or least > span:
        raise ValueError("least must be between 1 and span"):
    stretches = []
    current_start = start
        while current_start + span <=            stretch_end = current_start
            current_start += span
            if current_start - stretch_begin >= least:
                stretches.append((stretch_begin, current_start))
            current_start += rest):
    return stretches
```