The reference to the names of all Step elements used in the description of the Printed Circuit Assembly (PCA), the
unpopulated board or other related information (e.g., documentation). In manufacturing, this basic Step is often step
and repeated (nested) inside a larger step (called array, or sub-panel). This array step can be further nested into
another step (called a production panel). The Ecad element always contains at least one Step, but may contain
several, some basic ones and others nesting previous steps 翻译一下