"Frequency" used in place of "phase" in Seasonality tutorial

[dgmulf]

In the fourier_features() example algorithm on the Seasonality lesson of the Time Series course, the variable name freq is given to a parameter which takes units of days/cycle. This was confusing to me at first, because unless I'm mistaken, frequency typically refers to measurements given in inverse units (cycles/day), whereas period refers to time per cycle.