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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 Column(self, column_name):
 """Iterates over values of a given column. Args: column_name: A nome of the column to retrieve the values for. Yields: Values of the specified column. Raises: KeyError: If given column is not present in the table. """

    column_idx = None
    for idx, column in enumerate(self.header.columns):
      if column.name == column_name:
        column_idx = idx
        break

    if column_idx is None:
      raise KeyError("Column '{}' not found".format(column_name))

    for row in self.rows:
      yield row.values[column_idx]