def param_name(p):
    """Extract parameter name from attributes.

    Examples
    --------
    - ``fix_x`` -> ``x``
    - ``error_x`` -> ``x``
    - ``limit_x`` -> ``x``

    """
    prefix = ["limit_", "error_", "fix_"]
    for prf in prefix:
        if p.startswith(prf):
            i = len(prf)
            return p[i:]
    return p