@staticmethod
def getsize(lmax, mmax=None):
    """Returns the size of the array needed to store alm up to *lmax* and *mmax*

        Parameters
        ----------
        lmax : int
          The maximum l, defines the alm layout
        mmax : int, optional
          The maximum m, defines the alm layout. Default: lmax.

        Returns
        -------
        size : int
          The size of the array needed to store alm up to lmax, mmax.
        """
    if mmax is None or mmax < 0 or mmax > lmax:
        mmax = lmax
    return mmax * (2 * lmax + 1 - mmax) // 2 + lmax + 1
