@property<EOL><INDENT>def columns(self):<DEDENT>
return self._columns<EOL>
The list of columns in use.

:getter: Return the list of columns in use.
:setter: Set the columns to be loaded into, as well as their order. If
    loading from a file, these will be determined from the file header.
    Not necessary if you are loading into all columns, in the original
    order. The value must be a :code:`list` of names in the order that
    the fields of data will be presented in each row.

    Raises :class:`~giraffez.errors.GiraffeError` if :code:`field_names`
    is not a :code:`list`.

    Raises :class:`~giraffez.errors.GiraffeError` if the target table
    has not been set.
:type: :class:`~giraffez.types.Columns`