code: def from_uniform(
              cls, z, origin=(0, 0), step=(1, 1), formatter=numpy_formatter):
          
          z = np.ma.asarray(z, dtype=np.float64)
          # Check arguments.
          if z.ndim != 2:
              raise TypeError(
                  "'z' must be a 2D array but it a {:d}D array".format(z.ndim))
          if len(origin) != 2:
              raise TypeError(
                  "'origin' must be of length 2 but has length {:d}".format(
                      len(origin)))
          if len(step) != 2:
              raise TypeError(
                  "'step' must be of length 2 but has length {:d}".format(
                      len(step)))
          if any(s == 0 for s in step):
              raise ValueError(
                  "'step' must have non-zero values but is {:s}".format(
                      str(step)))
          # Convert to curvilinear format and call constructor.
          y, x = np.mgrid[
              origin[0]:(origin[0]+step[0]*z.shape[0]):step[0],
              origin[1]:(origin[1]+step[1]*z.shape[1]):step[1]]
          return cls(x, y, z, formatter)
docs: Construct a contour generator from a uniform grid.
  
          NOTE
          ----
          The default `origin` and `step` values is equivalent to calling
          :meth:`matplotlib.axes.Axes.contour` with only the `z` argument.
  
          Parameters
          ----------
          z : array_like
              The 2-dimensional uniform grid of data to compute contours for.
              Masked arrays are supported.
          origin : (number.Number, number.Number)
              The (x, y) coordinate of data point `z[0,0]`.
          step :  (number.Number, number.Number)
              The (x, y) distance between data points in `z`.
          formatter : callable
              A conversion function to convert from the internal `Matplotlib`_
              contour format to an external format.  See :ref:`formatters` for
              more information.
  
          Returns
          -------
          : :class:`QuadContourGenerator`
              Initialized contour generator.