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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 build_prefixes(namespaces=None):
 """Internal function takes a list of prefix, namespace uri tuples and generates a SPARQL PREFIX string. Args: namespaces(list):
 List of tuples, defaults to BIBFRAME and Schema.org Returns: string """

    if namespaces is None:
        namespaces = [
            ('bf', str(BIBFRAME)),
            ('schema', str(SCHEMA_ORG))
        ]
    output = "PREFIX {}: <{}>\n".format(
        namespaces[0][0],
        namespaces[0][1])
    if len(namespaces) == 1:
        return output
    else:
        for namespace in namespaces[1:]:
            output += "PREFIX  {}: <{}>\n".format(namespace[0], namespace[1])
    return output