<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def relpath(path, start=None):
 """ Return a relative file path to path either from the current directory or from an optional start directory. For storage objects, "path" and "start" are relative to storage root. "/" are not stripped on storage objects path. The ending slash is required on some storage to signify that target is a directory. Equivalent to "os.path.relpath". Args: path (path-like object):
 Path or URL. start (path-like object):
 Relative from this optional directory. Default to "os.curdir" for local files. Returns: str: Relative path. """

    relative = get_instance(path).relpath(path)
    if start:
        # Storage relative path
        # Replaces "\" by "/" for Windows.
        return os_path_relpath(relative, start=start).replace('\\', '/')
    return relative