<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _parametersAsIndex( self, ps ):
 """Private method to turn a parameter dict into a string suitable for keying a dict. ps: the parameters as a hash returns: a string key"""

        k = ""
        for p in sorted(ps.keys()):       # normalise the parameters
            v = ps[p]
            k = k + "{p}=[[{v}]];".format(p = p, v = v)
        return k