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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 _GetEventLogProviderKey(self, log_source):
 """Retrieves the Event Log provider key. Args: log_source (str):
 Event Log source. Returns: str: Event Log provider key or None if not available. Raises: RuntimeError: if more than one value is found in the database. """

    table_names = ['event_log_providers']
    column_names = ['event_log_provider_key']
    condition = 'log_source == "{0:s}"'.format(log_source)

    values_list = list(self._database_file.GetValues(
        table_names, column_names, condition))

    number_of_values = len(values_list)
    if number_of_values == 0:
      return None

    if number_of_values == 1:
      values = values_list[0]
      return values['event_log_provider_key']

    raise RuntimeError('More than one value found in database.')