<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def calc_qpin_v1(self):
 """Calculate the input discharge portions of the different response functions. Required derived parameters: |Nmb| |MaxQ| |DiffQ| Required flux sequence: |QIn| Calculated flux sequences: |QPIn| Examples: Initialize an arma model with three different response functions: Define the maximum discharge value of the respective response functions and their successive differences: The first six examples are performed for inflow values ranging from 0 to 12 m³/s: | ex. | qin | qpin | | 1 | 0.0 | 0.0 0.0 0.0 | | 2 | 1.0 | 1.0 0.0 0.0 | | 3 | 2.0 | 2.0 0.0 0.0 | | 4 | 4.0 | 2.0 2.0 0.0 | | 5 | 6.0 | 2.0 4.0 0.0 | | 6 | 12.0 | 2.0 4.0 6.0 | The following two additional examples are just supposed to demonstrate method |calc_qpin_v1| also functions properly if there is only one response function, wherefore total discharge does not need to be divided: | ex. | qin | qpin | | 7 | 0.0 | 0.0 | | 8 | 12.0 | 12.0 | """

    der = self.parameters.derived.fastaccess
    flu = self.sequences.fluxes.fastaccess
    for idx in range(der.nmb-1):
        if flu.qin < der.maxq[idx]:
            flu.qpin[idx] = 0.
        elif flu.qin < der.maxq[idx+1]:
            flu.qpin[idx] = flu.qin-der.maxq[idx]
        else:
            flu.qpin[idx] = der.diffq[idx]
    flu.qpin[der.nmb-1] = max(flu.qin-der.maxq[der.nmb-1], 0.)