.. class:: DesignMatrixBuilder

This is an opaque class that represents Patsy's knowledge about

how to build a design matrix. You get these objects from

:func:`design_matrix_builders`, and you pass them to

:func:`build_design_matrices`.

.. attribute:: design_info

This attribute gives metadata about the matrices that this

builder object can produce, in the form of a :class:`DesignInfo`

object.

.. automethod:: subset