How to use the nanopb.nanopb.generator.nanopb_generator.EncodedSize function in nanopb

if self.pbtype == 'MESSAGE':
            encsize = None
            if str(self.submsgname) in dependencies:
                submsg = dependencies[str(self.submsgname)]
                encsize = submsg.encoded_size(dependencies)
                if encsize is not None:
                    # Include submessage length prefix
                    encsize += varint_max_size(encsize.upperlimit())

            if encsize is None:
                # Submessage or its size cannot be found.
                # This can occur if submessage is defined in different
                # file, and it or its .options could not be found.
                # Instead of direct numeric value, reference the size that
                # has been #defined in the other file.
                encsize = EncodedSize(self.submsgname + 'size')

                # We will have to make a conservative assumption on the length
                # prefix size, though.
                encsize += 5

        elif self.pbtype in ['ENUM', 'UENUM']:
            if str(self.ctype) in dependencies:
                enumtype = dependencies[str(self.ctype)]
                encsize = enumtype.encoded_size()
            else:
                # Conservative assumption
                encsize = 10

        elif self.enc_size is None:
            raise RuntimeError("Could not determine encoded size for %s.%s"
                               % (self.struct_name, self.name))

def encoded_size(self, dependencies):
        '''Returns the size of the largest oneof field.'''
        largest = EncodedSize(0)
        for f in self.fields:
            size = EncodedSize(f.encoded_size(dependencies))
            if size.value is None:
                return None
            elif size.symbols:
                return None # Cannot resolve maximum of symbols
            elif size.value > largest.value:
                largest = size

        return largest

def encoded_size(self, dependencies):
        '''Returns the size of the largest oneof field.'''
        largest = EncodedSize(0)
        for f in self.fields:
            size = EncodedSize(f.encoded_size(dependencies))
            if size.value is None:
                return None
            elif size.symbols:
                return None # Cannot resolve maximum of symbols
            elif size.value > largest.value:
                largest = size

        return largest

def __add__(self, other):
        if isinstance(other, int):
            return EncodedSize(self.value + other, self.symbols)
        elif isinstance(other, strtypes + (Names,)):
            return EncodedSize(self.value, self.symbols + [str(other)])
        elif isinstance(other, EncodedSize):
            return EncodedSize(self.value + other.value, self.symbols + other.symbols)
        else:
            raise ValueError("Cannot add size: " + repr(other))

def __add__(self, other):
        if isinstance(other, int):
            return EncodedSize(self.value + other, self.symbols)
        elif isinstance(other, strtypes + (Names,)):
            return EncodedSize(self.value, self.symbols + [str(other)])
        elif isinstance(other, EncodedSize):
            return EncodedSize(self.value + other.value, self.symbols + other.symbols)
        else:
            raise ValueError("Cannot add size: " + repr(other))

def __add__(self, other):
        if isinstance(other, int):
            return EncodedSize(self.value + other, self.symbols)
        elif isinstance(other, strtypes + (Names,)):
            return EncodedSize(self.value, self.symbols + [str(other)])
        elif isinstance(other, EncodedSize):
            return EncodedSize(self.value + other.value, self.symbols + other.symbols)
        else:
            raise ValueError("Cannot add size: " + repr(other))

def encoded_size(self, dependencies):
        # We exclude extensions from the count, because they cannot be known
        # until runtime. Other option would be to return None here, but this
        # way the value remains useful if extensions are not used.
        return EncodedSize(0)

def __mul__(self, other):
        if isinstance(other, int):
            return EncodedSize(self.value * other, [str(other) + '*' + s for s in self.symbols])
        else:
            raise ValueError("Cannot multiply size: " + repr(other))

# prefix size, though.
                encsize += 5

        elif self.pbtype in ['ENUM', 'UENUM']:
            if str(self.ctype) in dependencies:
                enumtype = dependencies[str(self.ctype)]
                encsize = enumtype.encoded_size()
            else:
                # Conservative assumption
                encsize = 10

        elif self.enc_size is None:
            raise RuntimeError("Could not determine encoded size for %s.%s"
                               % (self.struct_name, self.name))
        else:
            encsize = EncodedSize(self.enc_size)

        encsize += varint_max_size(self.tag << 3) # Tag + wire type

        if self.rules == 'REPEATED':
            # Decoders must be always able to handle unpacked arrays.
            # Therefore we have to reserve space for it, even though
            # we emit packed arrays ourselves. For length of 1, packed
            # arrays are larger however so we need to add allowance
            # for the length byte.
            encsize *= self.max_count

            if self.max_count == 1:
                encsize += 1

        return encsize

def __add__(self, other):
        if isinstance(other, int):
            return EncodedSize(self.value + other, self.symbols)
        elif isinstance(other, strtypes + (Names,)):
            return EncodedSize(self.value, self.symbols + [str(other)])
        elif isinstance(other, EncodedSize):
            return EncodedSize(self.value + other.value, self.symbols + other.symbols)
        else:
            raise ValueError("Cannot add size: " + repr(other))