def add_to(self, other):
<EOL>if type(other) is MaterialPackage:<EOL><INDENT>if self.material == other.material:<EOL><INDENT>self.size_class_masses =self.size_class_masses + other.size_class_masses<EOL><DEDENT>else:  <EOL><INDENT>for size_class in other.material.size_classes:<EOL><INDENT>if size_class not in self.material.size_classes:<EOL><INDENT>raise Exception(<EOL>"<STR_LIT>" + other.material.name +<EOL>"<STR_LIT>" +<EOL>self.material.name +<EOL>"<STR_LIT>" + size_class +<EOL>"<STR_LIT>" + self.material.name + "<STR_LIT>")<EOL><DEDENT>self.add_to(<EOL>(size_class, other.get_size_class_mass(size_class)))<EOL><DEDENT><DEDENT><DEDENT>elif self._is_size_class_mass_tuple(other):<EOL><INDENT>size_class = other[<NUM_LIT:0>]<EOL>compound_index = self.material.get_size_class_index(size_class)<EOL>mass = other[<NUM_LIT:1>]<EOL>self.size_class_masses[compound_index] =self.size_class_masses[compound_index] + mass<EOL><DEDENT>else:<EOL><INDENT>raise TypeError("<STR_LIT>")<EOL><DEDENT>
Add another psd material package to this material package.

:param other: The other material package.