if (entry.getKey().equals(k0())) {
        assertEquals("entry.setValue() should return the old value", v0(), entry.setValue(null));
        break;
      }
    }
    expectReplacement(entry(k0(), (V) null));
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testSetValueWithNullValuesAbsent() {

      if (entry.getKey().equals(k0())) {
        assertEquals("entry.setValue() should return the old value", v0(), entry.setValue(null));
        break;
      }
    }
    expectReplacement(entry(k0(), (V) null));
  }

  @MapFeature.Require(value = SUPPORTS_PUT, absent = ALLOWS_NULL_VALUES)
  @CollectionSize.Require(absent = ZERO)
  public void testSetValueWithNullValuesAbsent() {

    //                                                                        ============
    protected String convertEmptyToNull(String value) {
        return (value != null && value.length() == 0) ? null : value;
    }

    // ===================================================================================

    return longBitsToDouble(bits);
  }

  /** Returns its argument if it is non-negative, zero if it is negative. */
  static double ensureNonNegative(double value) {
    checkArgument(!isNaN(value));
    return max(value, 0.0);
  }

  @VisibleForTesting static final long ONE_BITS = 0x3ff0000000000000L;

    }

    protected void assertObjectNotNull(String variableName, Object value) {
        if (variableName == null) {
            String msg = "The value should not be null: variableName=null value=" + value;
            throw new IllegalArgumentException(msg);
        }
        if (value == null) {
            String msg = "The value should not be null: variableName=" + variableName;

```

/// tip

The second argument to <a href="https://docs.python.org/3.8/library/os.html#os.getenv" class="external-link" target="_blank">`os.getenv()`</a> is the default value to return.

If not provided, it's `None` by default, here we provide `"World"` as the default value to use.

///

Then you could call that Python program:

//// tab | Linux, macOS, Windows Bash

<div class="termy">

```console

        }
        return list.toArray(new String[list.size()]);
    }

    public String getHeaderValue(final String name) {
        final String[] values = getHeaderValues(name);
        if (values.length == 0) {
            return null;
        }
        return values[0];
    }

     * be created automatically.
     *
     * @param output The file to serialize the settings to, must not be {@code null}.
     * @param options The options to use for serialization, may be {@code null} to use the default values.
     * @param settings The settings to serialize, must not be {@code null}.
     * @throws IOException If the settings could not be serialized.
     */

    // Squash into 224/4 Multicast and 240/4 Reserved space (i.e. 224/3).
    coercedHash |= 0xe0000000;

    // Fixup to avoid some "illegal" values. Currently the only potential
    // illegal value is 255.255.255.255.
    if (coercedHash == 0xffffffff) {
      coercedHash = 0xfffffffe;
    }

    return getInet4Address(Ints.toByteArray(coercedHash));
  }

  /**

    //                                                                        ============
    protected String convertEmptyToNull(String value) {
        return (value != null && value.length() == 0) ? null : value;
    }

    // ===================================================================================