def stride_chainid_to_pdb_chainid(stride_chainid):
    """
    Convert a STRIDE chainid to a PDB chainid.
    STRIDE uses '-' for a 'blank' chainid while PDB uses ' ' (space).
    So all this does is return the stride_chainid unless it is '-', then
    it returns ' '.

    Parameters:
        stride_chainid - the STRIDE chain identifier
    Return value:
        PDB chain identifier corresponding to supplied stride_chainid
    """
    if stride_chainid == '-':
        return ' '
    else:
        return stride_chainid