To further illustrate SingleGraph, consider the example in Figure where we create SMIRKS for the carbon-carbon bond in ethanol. This is implemented in the code snippet above. The molecule object can be created from a SMILES ('CC'), where the carbons are at index 0 and 1. We then decide how many layers to include. Zero layers would only include the carbon-carbon bond, then one layer would add the hydrogens and oxygen immediately bonded to those carbons. If we specify two layers the hydrogen in the alcohol group would also be added; for ethanol this is equivalent to specifying 'all' atoms. Then we can output the graph as a complex SMIRKS pattern (i.e. [#6H3X4x0!r+0A:1]-;!@[#6H2X4x0!r+0A:2]) or in the compressed form with only atomic numbers (i.e. [#6:1]-;@[#6:2]).