def get_element_mass(self, element):
result = numpy.zeros(<NUM_LIT:1>)<EOL>for compound in self.material.compounds:<EOL><INDENT>result += self.get_compound_mass(compound) *numpy.array(stoich.element_mass_fractions(compound, [element]))<EOL><DEDENT>return result[<NUM_LIT:0>]<EOL>
Determine the mass of the specified elements in the package.

:returns: Masses. [kg]