code: def extract_xyz_matrix_from_chain(self, chain_id, atoms_of_interest = []):
          '''Create a pandas coordinates dataframe from the lines in the specified chain.'''
          chains = [l[21] for l in self.structure_lines if len(l) > 21]
          chain_lines = [l for l in self.structure_lines if len(l) > 21 and l[21] == chain_id]
          return PDB.extract_xyz_matrix_from_pdb(chain_lines, atoms_of_interest = atoms_of_interest, include_all_columns = Truef extract_xyz_matrix_from_chain(self, chain_id, atoms_of_interest = []):
          '''Create a pandas coordinates dataframe from the lines in the specified chain.'''
          chains = [l[21] for l in self.structure_lines if len(l) > 21]
          chain_lines = [l for l in self.structure_lines if len(l) > 21 and l[21] == chain_id]
          return PDB.extract_xyz_matrix_from_pdb(chain_lines, atoms_of_interest = atoms_of_interest, include_all_columns = True)
docs: Create a pandas coordinates dataframe from the lines in the specified chain.