Calculates formal charge for each atom.
		Takes:
			* mol * - mol file in rdkit environment
		Output:
			* formal_charges * - list of charges

def calculate_formal_charge(self,mol):
		"""Calculates formal charge for each atom.
		Takes:
			* mol * - mol file in rdkit environment
		Output:
			* formal_charges * - list of charges
		"""
		formal_charges = []
		for atom in mol.GetAtoms():
			formal_charges.append(atom.GetFormalCharge())
		return formal_charges