code: def convert_species_to_atomic_nums(s):
      PERIODIC_TABLE = {"H": 1, "C": 6, "N": 7, "O": 8}
      res = []
      for k in s:
          res.append(PERIODIC_TABLE[k])
      return np.array(res, dtype=np.float32)
  
file_path: deepchem/examples/roitberg/roitberg.py
imports: import numpy
  import os
  import tensorflow
  import deepchem
  import pyanitools
  import app
label_desc: Use image node_id 1 for calling a global function with example usage: convert_species_to_atomic_nums(s) and returns: np