'Initialize all IS_NOT_IN_DB to allow override of
both original and duplicate value
@param field: the Field
@param o: the original value
@param d: the duplicate value'

@staticmethod
def init_requires(field, o, d):

    allowed_override = [str(o), str(d)]
    requires = field.requires
    if (field.unique and (not requires)):
        field.requires = IS_NOT_IN_DB(current.db, str(field), allowed_override=allowed_override)
    else:
        if (not isinstance(requires, (list, tuple))):
            requires = [requires]
        for r in requires:
            if hasattr(r, 'allowed_override'):
                r.allowed_override = allowed_override
            if (hasattr(r, 'other') and hasattr(r.other, 'allowed_override')):
                r.other.allowed_override = allowed_override
    return
