Pandas DataFrame: Replace 'Flash' with 'Modified' in 'Column1'

This code applies a lambda function to each value in the 'Column1' of the DataFrame df. The lambda function checks if the value is equal to 'Flash'. If it is, the lambda function replaces the value with 'Modified'. If it isn't, the lambda function leaves the value unchanged. The result is a modified 'Column1' in the DataFrame df.