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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:

def _read_field(self):
        '''
        Read a single byte for field type, then read the value.
        '''
        ftype = self._input[self._pos]
        self._pos += 1

        reader = self.field_type_map.get(ftype)
        if reader:
            return reader(self)

        raise Reader.FieldError('Unknown field type %s', ftype)