The Aligner specifies the operation that will be applied to the
data points in each alignment period in a time series. Except for
ALIGN_NONE, which specifies that no operation be applied, each
alignment operation replaces the set of data values in each
alignment period with a single value: the result of applying the
operation to the data values. An aligned time series has a single
data value at the end of each alignment_period.
An alignment operation can change the data type of the values, too.
For example, if you apply a counting operation to boolean values,
the data value_type in the original time series is BOOLEAN,
but the value_type in the aligned result is INT64.
