<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def _overlap(y,yr,psd):
 """ returns the detector noise weighted inner product """

    yyr  = _inner_product(y,yr,psd)
    yy   = _inner_product(y,y,psd)
    yryr = _inner_product(yr,yr,psd)
    olap = yyr/np.sqrt(yy*yryr)
    return olap