qiskit.QuantumCircuit and qiskit.QuantumCircuit.draw()

The first time I create a two qubits, two bits circuit and draw it the output is:

q0_0 
q0_1 
c0_0 
c0_1 

Each subsequent time I run my script (even after clearing all the variables) I get the following:

q1_0
q1_1 
c1_0 
c1_1 
. 
. 
. 
qn_0 
qn_1 
cn_0 
cn_1 

The number next to the qubit or classical bit increases every time. Is this a bug, is there a way to avoid this?

I am using Qiskit 0.19.6.

from qiskit import QuantumCircuit, QuantumRegister, ClassicalRegister

qr = QuantumRegister(2, 'q')
cr = ClassicalRegister(2, 'c')
circuit = QuantumCircuit(qr, cr)
circuit.draw()