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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 filter_select_columns_intensity(df, prefix, columns):
 """ Filter dataframe to include specified columns, retaining any Intensity columns. """

    # Note: I use %s.+ (not %s.*) so it forces a match with the prefix string, ONLY if it is followed by something.
    return df.filter(regex='^(%s.+|%s)$' % (prefix, '|'.join(columns)) )