Represents the "YStep" entry of the type 1 pattern dictionary object.

It is a required entry defined as part of the PDF 1.0 specification.

It contains a double representing a PDF numeric object.

It should have a positive value.

For definitive details see:.

The ISO PDF Specification, ISO 32000-1:2008 PDF 1.7; Table: 75, page 175.

The ISO PDF Specification, ISO 32000-2:2017 PDF 2.0; Table: 74, page 218.

YStep defines the vertical offset in pattern space between successive rows of the tiled pattern. Like XStep, it may differ from the BBox height to produce gaps or overlaps in the vertical direction.