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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def _group_similar(items: List[T], comparer: Callable[[T, T], bool]) -> List[List[T]]: """Combines similar items into groups. Args: items: The list of items to group. comparer: Determines if two items are similar. Returns: A list of groups of items. """

    groups = []  # type: List[List[T]]
    used = set()  # type: Set[int]
    for i in range(len(items)):
        if i not in used:
            group = [items[i]]
            for j in range(i + 1, len(items)):
                if j not in used and comparer(items[i], items[j]):
                    used.add(j)
                    group.append(items[j])
            groups.append(group)
    return groups