A column with a semantic tag attached.
.. attribute:: field
Required. Identifies the column.
A column can be tagged with a InfoType to use the relevant
public dataset as a statistical model of population, if
available. We currently support US ZIP codes, region codes,
ages and genders. To programmatically obtain the list of
supported InfoTypes, use ListInfoTypes with the
supported_by=RISK_ANALYSIS filter.
If no semantic tag is indicated, we infer the statistical
model from the distribution of values in the input data
