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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 GetMetadataAttribute(self, attribute_name):
 """Retrieves the metadata attribute. Args: attribute_name (str):
 name of the metadata attribute. Returns: str: the metadata attribute or None. Raises: RuntimeError: if more than one value is found in the database. """

    table_name = 'metadata'

    has_table = self._database_file.HasTable(table_name)
    if not has_table:
      return None

    column_names = ['value']
    condition = 'name == "{0:s}"'.format(attribute_name)

    values = list(self._database_file.GetValues(
        [table_name], column_names, condition))

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

    if number_of_values == 1:
      return values[0]['value']

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