int GetFragmentNumber() const
Return the fragment number property of a residue. Fragment numbers are integer indices that define connected components of a macromolecule. When reading from a PDB file, the first atom is placed in fragment number 1. Each time a ``TER'', ``END'' or ``ENDM'' record is encountered within a single connection table, the fragment number is incremented. Similarly, when writing a PDB file, a TER record is written between any consecutive pair of atoms with different fragment numbers. The fragment number property may be set using the OEResidue::SetFragment number property.