Function get_residues 

pub fn get_residues(pdb: &PDB, target: Vec<isize>) -> Vec<&Residue>

Retrieves specific residues from a PDB structure based on their serial numbers.

Arguments

• pdb - A reference to a pdbtbx::PDB structure representing the entire protein.
• target - A vector of isize values representing the serial numbers of the residues to retrieve.

Returns

A Vec<&Residue> containing references to the residues whose serial numbers match those in the target vector.

Notes

• This function performs a linear search through all residues in the PDB structure.
• The order of residues in the result vector matches the order they appear in the PDB structure, not necessarily the order of serial numbers in the target vector.
• If a serial number in target doesn’t match any residue in the PDB, it is simply ignored.