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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 _get_namespaces(apiserver_url, name=""):
    '''Get namespace is namespace is defined otherwise return all namespaces'''
    # Prepare URL
    url = "{0}/api/v1/namespaces/{1}".format(apiserver_url, name)
    # Make request
    ret = http.query(url)
    if ret.get("body"):
        return salt.utils.json.loads(ret.get("body"))
    else:
        return None