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 circle(self,x,y,r):
		for x_offset in range(-r,r+1):
			for y_offset in range(-r,r+1):
				if sqrt(x_offset**2+y_offset**2)<r:
					self.board[x+x_offset,y+y_offset] = self.color