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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 sampling_query(sql, fields=None, count=5, sampling=None):
 """Returns a sampling query for the SQL object. Args: sql: the SQL object to sample fields: an optional list of field names to retrieve. count: an optional count of rows to retrieve which is used if a specific sampling is not specified. sampling: an optional sampling strategy to apply to the table. Returns: A SQL query string for sampling the input sql. """

    if sampling is None:
      sampling = Sampling.default(count=count, fields=fields)
    return sampling(sql)