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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 add_definitions(definitions, operations):
 """ Add definitions to swagger. """

    for definition_schema in iter_definitions(definitions, operations):
        if definition_schema is None:
            continue
        if isinstance(definition_schema, str):
            continue

        for name, schema in iter_schemas(definition_schema):
            definitions.setdefault(name, swagger.Schema(schema))