all frequency offset in pandas

Alias    Description
B        business day frequency
C        custom business day frequency
D        calendar day frequency
W        weekly frequency
M        month end frequency
SM       semi-month end frequency (15th and end of month)
BM       business month end frequency
CBM      custom business month end frequency
MS       month start frequency
SMS      semi-month start frequency (1st and 15th)
BMS      business month start frequency
CBMS     custom business month start frequency
Q        quarter end frequency
BQ       business quarter end frequency
QS       quarter start frequency
BQS      business quarter start frequency
A, Y     year end frequency
BA, BY   business year end frequency
AS, YS   year start frequency
BAS, BYS business year start frequency
BH       business hour frequency
H        hourly frequency
T, min   minutely frequency
S        secondly frequency
L, ms    milliseconds
U, us    microseconds
N        nanoseconds

Here is what the above code is Doing:
1. Creating a date range from Jan 1, 2017 to Jan 1, 2018
2. Creating a series of random numbers
3. Creating a time stamp index
4. Creating a dataframe with the time stamp index and the random numbers
5. Resampling the dataframe to a monthly frequency
6. Plotting the dataframe