def tensor_mul(*a):
 if (not a):
  return TensMul.from_data(S.One, [], [], [])
 t = a[0]
 for tx in a[1:]:
  t = (t * tx)
 return t

def tensor_mul ( * a ) : if ( not a ) : return TensMul . from_data ( S . One , [ ] , [ ] , [ ] ) t = a [ 0 ] for tx in a [ 1 : ] : t = ( t * tx ) return t
product of tensors .