Check if the parent info is correct. If an individual is not present in file raise exeption.

        Input: An id that represents a parent
               father = True/False

        Raises SyntaxError if
            The parent id is not present
            The gender of the parent is wrong.

def check_parent(self, parent_id, father = False):
        """
        Check if the parent info is correct. If an individual is not present in file raise exeption.

        Input: An id that represents a parent
               father = True/False

        Raises SyntaxError if
            The parent id is not present
            The gender of the parent is wrong.
        """
        self.logger.debug("Checking parent {0}".format(parent_id))
        if parent_id != '0':
            if parent_id not in self.individuals:
                raise PedigreeError(self.family_id, parent_id, 
                                    'Parent is not in family.')
            if father:
                if self.individuals[parent_id].sex != 1:
                    raise PedigreeError(self.family_id, parent_id, 
                                        'Father is not specified as male.')
            else:
                if self.individuals[parent_id].sex != 2:
                    raise PedigreeError(self.family_id, parent_id, 
                                        'Mother is not specified as female.')
        return