Columns with BasedReal conversions and truncatures

Enforce data homogeneity

class BasedColumn(Column):
   def __init__(self, *args, **kwargs):
       assert all(type(v) is type(args[0][0]) for v in args[0])
       self.values_type = type(v)
   def astype(self, dtype, *args, **kwargs):
       if issubclass(dtype, BasedReal):
           return np.vectorize(...)(self)
       else:
           return super().astype(dtype, *args, **kwargs)
   def truncate(self, ...):
       return np.vectorize(...)(self)