<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def force_unicode(value):
 """ Forces a bytestring to become a Unicode string. """

    if IS_PY3:
        # Python 3.X
        if isinstance(value, bytes):
            value = value.decode('utf-8', errors='replace')
        elif not isinstance(value, str):
            value = str(value)
    else:
        # Python 2.X
        if isinstance(value, str):
            value = value.decode('utf-8', 'replace')
        elif not isinstance(value, basestring):  # NOQA: F821
            value = unicode(value)  # NOQA: F821

    return value