This method returns the number of implicit H's on the atom. 
Depending on where the molecule was read from this may be NULL or an integer
greater than or equal to 0
Get the implicit hydrogen count for the atom.
This method returns the number of implicit H's on the atom. 
Depending on where the molecule was read from this may be NULL or an integer
greater than or equal to 0
get.hydrogen.count(atom)The atom to query
An integer representing the hydrogen count