code: def select(self, column, agg=None, _as=None, distinct=False):
          
          if agg and not _as:
              raise ValueError("Aggregate colunns require `_as` to be specified")
          if column is False:
              self._selects = {}
          else:
              self._selects.setdefault((_as or column), (column, agg, _as, distinct))
docs: What columnns to select in query.
          :column should be a column name or equation to produce column **not** aggregated
          :agg should be a valid aggregate method used to producte the figure
          :_as should be a string used to represent the column. Required when agg present