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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 schema_resolve_refs(schema, ref_resolver=None, root=None):
 """ Helper method for decoding references. Self-references are resolved automatically; other references are resolved using a callback function. :param object schema: :param callable ref_resolver: :param None root: :return: """

    # FIXME more stable implementation that only attempts to resolve {"$ref"} objects where they are allowed.
    if isinstance(schema, dict):
        if len(schema) == 1 and "$ref" in schema and isinstance(schema["$ref"], six.string_types):
            reference = schema["$ref"]
            if reference.startswith("#"):
                # TODO should also resolve any paths within the reference, which would need to be deferred.
                return root
            return ref_resolver(reference)

        resolved = {}
        for k, v in schema.items():
            resolved[k] = schema_resolve_refs(v,
                                              ref_resolver=ref_resolver,
                                              root=root if root is not None else resolved)
        return resolved
    if isinstance(schema, (list, tuple)):
        return [schema_resolve_refs(v, ref_resolver=ref_resolver, root=root) for v in schema]
    return schema