def remove(self, elem):
        """Remove a requirement.

        :param elem: a string or :class:`Requirement` instance.
        """
        if isinstance(elem, text_type):
            for requirement in self:
                if requirement.package == elem:
                    return super(Requirements, self).remove(requirement)
        return super(Requirements, self).remove(elem)
def inc_c(self, ind):
        r, c = self.row_col(ind)
        c += 1
        if c == self.nc:
            c = 0
        if r == (self.nr - 1) and c == (self.nc - 1):
            c = 0
        return self.indx(r, c)